JP4916271B2 - Solid-state imaging device and electronic information device - Google Patents

Description

  The present invention relates to a solid-state imaging device capable of imaging by photoelectrically converting incident light (subject light) by each light-receiving unit (each pixel unit), and a monitoring camera for taking an image using the solid-state imaging device as an imaging unit The present invention relates to an electronic information device such as a door phone camera, a vehicle-mounted camera, a television phone camera, and a mobile phone camera.

  Conventionally, various solid-state imaging devices such as a solid-state imaging device for a CCD camera in which this type of solid-state imaging device (Charge Coupled Device: hereinafter referred to as a CCD) is incorporated have been proposed.

  Such a solid-state imaging device (CCD camera) using a CCD is used for various purposes, such as when shooting a subject in a dark room or shooting outdoors in a sunny room. Range from a few lux to hundreds of thousands of lux. In particular, when intense light such as sunlight is directly projected on the screen, the subject becomes extremely bright.

  The CCD camera includes a photoelectric conversion element such as a photodiode (light receiving unit) that photoelectrically converts incident light, a vertical charge transfer unit that transfers signal charges read from the photoelectric conversion element in the vertical direction, and the vertical charge. A horizontal charge transfer unit that horizontally transfers the signal charge from the transfer unit, and a signal output unit that detects the signal charge from the horizontal charge transfer unit and outputs the signal as an imaging signal to the outside. There is an upper limit to the amount of charge that can be handled by the photoelectric conversion element, the vertical charge transfer unit, and the horizontal charge transfer unit.

  In such a CCD camera, when light is incident on a photodiode constituting each pixel portion, the light is photoelectrically converted into a signal charge according to the amount of light, and the signal charge is accumulated in the photodiode. However, when intense light such as sunlight is irradiated onto the photodiode and the photoelectrically converted charge signal exceeds the capacity of the photodiode, the charge overflows in the vertical shift register arranged adjacent to the photodiode. I will put it out. In addition, when the capacity of the vertical shift register is exceeded, electric charges overflow into the vertical shift registers arranged above and below in the vertical shift register. Furthermore, when the capacity of the horizontal shift register is exceeded, charges overflow into the horizontal shift registers arranged on the left and right in the horizontal shift register. As a result, there is a concern that the screen may turn white and problems such as image distortion may occur.

  Therefore, in order to image a very bright subject, it is necessary to perform exposure control so as not to exceed the upper limits of the photodiode capacity, vertical shift register capacity, horizontal shift register capacity, and the like that constitute the CCD. For this reason, conventionally, exposure control is performed by providing a mechanical iris for passing light on a lens disposed in front of the CCD and changing the hole diameter in accordance with the illuminance of the subject.

  However, providing a mechanical iris is costly, and further, it is difficult to reduce the size of the mechanical iris. Therefore, an electronic shutter function for outputting signal charges from the photoelectric conversion element is provided, and depending on the illuminance of the subject. An increasing number of EE (Electric Exposure) type CCD cameras control exposure by changing the electronic shutter time (exposure time).

  Furthermore, in order to avoid the occurrence of the above-mentioned problems caused by intense light such as sunlight entering the CCD, an overflow drain (OFD) is provided on the base of the CCD, and the OFD voltage is adjusted to thereby reduce the photo A configuration is also used in which charges accumulated more than necessary in the diode are caused to flow to the CCD substrate via the OFD. Such an OFD voltage is adjusted to a voltage that does not cause a problem such as blooming in a normal subject and can sufficiently secure a saturation level.

  Further, in such a CCD camera, an effective pixel unit in which a plurality of photoelectric conversion elements that photoelectrically convert incident light are arranged and an electrical signal (imaging signal) corresponding to a subject image is output as an effective video signal, and the effective pixel And an OB section provided around the section, in which a plurality of photoelectric conversion elements covered with a light shielding member are arranged and an electric signal used as an optical black reference is output as an OB (optical black) level signal. The video signal processing unit performs various kinds of signal processing on the effective video signal from the effective pixel unit using the OB level signal from the OB unit as a black level reference.

  However, when excessive light is incident on the CCD, the signal charges generated in the photoelectric conversion elements such as photodiodes constituting the effective pixel portion exceed the capacity of the corresponding vertical shift register, and the horizontal shift register During the scanning period, the signal overflows to the horizontal shift register, and the signal charge also overflows to the OB portion, which is beyond the capacity of the horizontal shift register and is originally light-shielded and does not have photoelectrically converted signal charges. End up.

  As a result, the black level (OB level) of the OB signal output from the OB portion becomes higher than that during normal operation and becomes a bright level different from the optical black reference, so that there is no gradation difference in the dark portion. As a result, the image display becomes dark and sunk overall. Further, when the signal charge overflows to the OB portion side, the optical black reference becomes a brighter level, so that the OB signal level (OB level) and the effective image corresponding to the subject image from the effective pixel portion are obtained. There is no difference in level with the video signal, and a black image is displayed as in the dark.

  In the EE type CCD camera that controls exposure by controlling the electronic shutter time based on the illuminance of the subject described above, since the F value of the lens is not changed without using a mechanical iris, intense light such as sunlight is generated. When direct imaging is performed, extremely strong light is irradiated onto the imaging surface of the CCD. For this reason, incident light is photoelectrically converted by the photodiode to generate a large amount of signal charge, and this signal charge is extremely large, which far exceeds each capacitance of the photodiode, vertical shift register, horizontal shift register, etc. Therefore, trouble occurs at the time of the phenomenon.

  As a countermeasure for this, for example, a conventional imaging method as disclosed in Patent Document 1 can be cited.

In the conventional CCD camera disclosed in Patent Document 1, in an EE type CCD camera that controls exposure by variably controlling the electronic shutter speed, the electronic shutter time is shorter than a certain time (electronic shutter). When the speed is higher than a certain speed), the output voltage from the OFD voltage setting circuit is increased by a predetermined voltage value, and the signal charge accumulated in the photodiode is caused to flow to the substrate side. As a result, the amount of signal charge accumulated in each photodiode is reduced, and the above-described problems are avoided.
JP 2003-309762 A

  However, the conventional CCD camera disclosed in Patent Document 1 has the following problems.

  In this conventional CCD camera, when the electronic shutter time is shorter than a certain time, the output voltage of the OFD voltage setting circuit is increased by a predetermined voltage value, but excessive light such as sunlight is incident on the CCD. In addition, in order to determine whether or not the level difference between the level of the OB signal (OB level) and the effective video signal corresponding to the subject image from the effective pixel portion is a constant level, the output voltage is held at a constant level. The electronic shutter time is adjusted to be longer or shorter. For this reason, it takes time until the electronic shutter is adjusted after the light is incident. Thereafter, since the output voltage from the OFD voltage setting circuit is adjusted to be higher when the electronic shutter time is shorter than a predetermined time, it takes time to increase the OFD voltage after light is incident. Even during that time, excessive light such as sunlight is incident on the CCD, and signal charges that have undergone photoelectric conversion are generated, causing problems such as image distortion beyond each capacitance such as photodiode capacitance. There are concerns about the occurrence.

  Further, in the conventional CCD camera, there is a level difference between the OB signal level (OB level) and the effective video signal corresponding to the subject image from the effective pixel unit by a predetermined value, and it is determined that the output voltage is a certain level or more. In such a case, the electronic shutter time is adjusted to be short (the electronic shutter speed is adjusted to be fast). Therefore, when the electronic shutter time becomes shorter than a certain time, the output voltage of the OFD voltage setting circuit is set high, and a problem can be avoided.

  However, although intense light is incident, the signal charge overflows in the OB portion, and the level difference between the OB signal level (OB level) and the effective video signal corresponding to the subject image from the effective pixel portion is predetermined. When the output voltage is lower than a certain level and the output voltage is below a certain level, the output voltage is held at a certain level, so that the electronic shutter time becomes longer (the electronic shutter speed becomes slower) and the shutter operation is not performed. Will be controlled. Therefore, the electronic shutter time does not become a fixed time for increasing the output voltage of the OFD voltage setting circuit, and control for increasing the output voltage of the OFD voltage setting circuit may not be performed.

  Furthermore, even when there is no level difference between the OB signal level (OB level) and the effective video signal corresponding to the subject image from the effective pixel portion, the electronic shutter time is increased because the output voltage is held at a constant level. Control is performed so that the shutter operation is not performed. Therefore, the electronic shutter time does not become a fixed time for increasing the output voltage of the OFD voltage setting circuit, and control for increasing the output voltage of the OFD voltage setting circuit may not be performed.

  The present invention solves the above-described conventional problems, and a solid-state imaging device capable of suppressing the occurrence of image defects when irradiated with intense light such as sunlight, and the solid-state imaging device for an imaging unit. The purpose is to provide electronic information devices that have been used.

The solid-state imaging device according to the present invention obtains a video signal based on a black level signal photoelectrically converted by the solid-state imaging device with respect to an imaging signal photoelectrically converted by the solid-state imaging device provided on the base. in, on the basis of the imaging signal and said black level signal, or there is no level difference in the image pickup signal and said black level signal, or the level difference of the image pickup signal and said black level signal is below a certain level not And a determination result of the determination circuit indicates that there is no level difference between the imaging signal and the black level signal, or that the level difference between the imaging signal and the black level signal is a certain level or less. in the case shown, to set the excessive signal charge by a predetermined voltage than its normal set voltage OFD (overflow drain) voltage to flow from the photoelectric conversion elements of the solid imaging element to the base board side high OFD A pressure setting circuit, said one determination circuit of the determination result is no level difference in the image pickup signal and said black level signal or, if the level difference between the image pickup signal and said black level signal is below a certain level, the photoelectric its normal or long the set predetermined time than the set time an electronic shutter pulse application time for discharging the signal charges to the substrate board side from the conversion element, or the electronic shutter speed, the predetermined speed than the electronic shutter speed of normal exposure control And an exposure control unit that sets the speed as fast as possible, thereby achieving the above object.

The solid-state imaging device according to the present invention obtains a video signal based on a black level signal photoelectrically converted by the solid-state imaging device with respect to an imaging signal photoelectrically converted by the solid-state imaging device provided on the base. in, on the basis of the imaging signal and said black level signal, or there is no level difference in the image pickup signal and said black level signal, or the level difference of the image pickup signal and said black level signal is below a certain level not And a determination result of the determination circuit indicates that there is no level difference between the imaging signal and the black level signal, or that the level difference between the imaging signal and the black level signal is a certain level or less. case, or also set a predetermined time longer than the photoelectric conversion element electronic shutter pulse application time for discharging the signal charges to the substrate platen side its normal setting time of the solid-state image capturing device or an electronic shutter speed, showing , Than the electronic shutter speed of normal exposure control are those with an exposure control unit that sets higher predetermined speed, the object can be achieved.

The solid-state imaging device according to the present invention obtains a video signal based on a black level signal photoelectrically converted by the solid-state imaging device with respect to an imaging signal photoelectrically converted by the solid-state imaging device provided on the base. in, on the basis of the imaging signal and said black level signal, or there is no level difference in the image pickup signal and said black level signal, or the level difference of the image pickup signal and said black level signal is below a certain level not And a determination result of the determination circuit indicates that there is no level difference between the imaging signal and the black level signal, or that the level difference between the imaging signal and the black level signal is a certain level or less. case, which was equipped with OFD voltage setting circuit for setting higher by a predetermined voltage than its normal set voltage OFD voltage for flowing more than necessary signal charges from the photoelectric conversion elements of the solid imaging element to the base plate side shown Ri, the object is achieved.

The solid-state imaging device according to the present invention obtains a video signal based on a black level signal photoelectrically converted by the solid-state imaging device with respect to an imaging signal photoelectrically converted by the solid-state imaging device provided on the base. , Whether there is no level difference between the imaging signal and the black level signal based on the imaging signal and the black level signal, or whether the level difference between the imaging signal and the black level signal is a certain level or less. And a determination result of the determination circuit indicates that there is no level difference between the imaging signal and the black level signal, or that the level difference between the imaging signal and the black level signal is a certain level or less. In this case, an OFD (overflow drain) voltage for causing an excessive signal charge to flow from the photoelectric conversion element of the solid-state imaging device to the base side is set higher by a predetermined voltage than the normal setting voltage. If the determination result of the pressure setting circuit and the determination circuit is that there is no level difference between the imaging signal and the black level signal, or the level difference between the imaging signal and the black level signal is a certain level or less, The electronic shutter pulse application time for discharging the signal charge from the conversion element to the substrate side is set longer than the normal setting time by a predetermined time, or the electronic shutter speed is set to a predetermined speed higher than the electronic shutter speed by the normal exposure control. and a exposure control unit that sets quickly, the determination result of the decision circuit or no level difference in the image signal and the black level signal, a level difference of the image pickup signal and said black level signal at a constant level or less to indicate that, at first the OFD voltage by said OFD voltage setting circuit is set high by the predetermined voltage, then the electronic shutter pulse application by the exposure control unit The or just long set the predetermined time, the electronic shutter speed is intended to set as fast as the predetermined speed, the object can be achieved.

Further preferably, in the solid-state imaging device of the present invention, the OFD voltage setting circuit sets the OFD voltage higher by the predetermined voltage, and the exposure control unit sets the electronic shutter pulse application time longer by the predetermined time. Alternatively, in a state where the electronic shutter speed is set to be faster by the predetermined speed, the determination result of the determination circuit further indicates that there is no level difference between the imaging signal and the black level signal, or the imaging signal and the black level When the signal level difference indicates a certain level or less, it is determined that the signal is dark and the exposure control unit sets the electronic shutter pulse application time to be shorter by a predetermined time or the electronic shutter speed Is set slower by a predetermined speed, and then the OFD voltage is set lower by a predetermined voltage by the OFD voltage setting circuit. In addition, the solid-state imaging device of the present invention is a solid-state device that obtains a video signal based on a black level signal photoelectrically converted by the solid-state imaging device with respect to an imaging signal photoelectrically converted by the solid-state imaging device provided on the base In the imaging apparatus, there is no level difference between the imaging signal and the black level signal based on the imaging signal and the black level signal, or the level difference between the imaging signal and the black level signal is equal to or less than a certain level. And the determination result of the determination circuit is that there is no level difference between the imaging signal and the black level signal, or the level difference between the imaging signal and the black level signal is below a certain level. In this case, an OFD (overflow drain) voltage for flowing more signal charge than necessary from the photoelectric conversion element of the solid-state imaging device to the base side is set higher than the normal setting voltage by a predetermined voltage. The determination result of the FD voltage setting circuit and the determination circuit indicates that there is no level difference between the imaging signal and the black level signal, or the level difference between the imaging signal and the black level signal is equal to or lower than a certain level. The electronic shutter pulse application time for discharging the signal charge from the photoelectric conversion element to the substrate side is set longer than the normal setting time by a predetermined time, or the electronic shutter speed is set at a predetermined speed higher than the electronic shutter speed by the normal exposure control. and a exposure control unit for setting as quickly, or the OFD voltage set higher by the predetermined voltage by the OFD voltage setting circuit, the electronic shutter pulse application time is set longer by the predetermined time by the exposure control unit , Les the electronic shutter speed in a state of setting as quickly as the predetermined speed, further, the determination result is the imaging signal and said black level signal of the decision circuit The exposure control unit determines that the image is dark and the electronic shutter pulse application time is determined by the exposure control unit when the difference between the image signal and the black level signal is equal to or less than a certain level. Is set shorter by a predetermined time, or the electronic shutter speed is set lower by a predetermined speed, and then the OFD voltage setting circuit sets the OFD voltage lower by a predetermined voltage. Achieved.

   Further preferably, the solid-state imaging device in the solid-state imaging device of the present invention includes an effective pixel unit in which a plurality of the photoelectric conversion elements are arranged and each imaging signal corresponding to each pixel of the subject image is output as an effective video signal. A plurality of photoelectric conversion elements covered with a light-shielding member, and an OB (optical black) portion that outputs the black level signal used as an optical black level reference.

   Still preferably, in a solid-state imaging device according to the present invention, the solid-state imaging device includes a vertical transfer unit that transfers signal charges read from the photoelectric conversion elements in a vertical direction, and a signal charge from the vertical transfer unit horizontally. It further includes a horizontal transfer unit that transfers charges in the direction, and a charge detection unit that outputs signal charges from the horizontal transfer unit as an imaging signal.

   Further preferably, in the solid-state imaging device according to the present invention, for the effective video signal from the effective pixel unit, the video signal obtained by performing various signal processing for display on the video signal obtained based on the black level signal from the OB unit A signal processing unit is further included.

Further preferably, in the solid-state imaging device according to the present invention, the solid-state imaging device further includes a detection circuit that detects the effective video signal and the black level signal and detects a level difference therebetween, and the detection circuit is one of the determination circuits. Also serves as a department .

Further, preferably, in a solid-state imaging device of the present invention, the determination circuit is the detection circuit, the detection circuit, the or there are no level differences in the imaging signal and the black level signal, the image pickup signal and the It is detected whether the level difference of the black level signal is below a certain level.

Further preferably, in the solid-state imaging device of the present invention, the exposure control unit also serves as a part of the determination circuit, and the exposure control unit receives the detection of a level difference by the detection circuit, and the exposure control unit It is detected whether there is no level difference between the signal and the black level signal, or whether the level difference between the imaging signal and the black level signal is below a certain level.

   Further preferably, in the solid-state imaging device according to the present invention, the solid-state imaging device further includes a mechanical iris that can control the amount of light incident on the solid-state imaging element by changing a diameter of the aperture, and the exposure control unit includes the black The aperture diameter of the mechanical iris is controlled based on the level signal.

   Further preferably, in the solid-state imaging device of the present invention, the OFD voltage is controlled by the OFD voltage setting circuit from the time of power-on.

   Further preferably, in the solid-state imaging device of the present invention, the electronic shutter operation is controlled by the exposure control unit from the time of power-on.

   Further, preferably, when the level difference in the solid-state imaging device of the present invention is equal to or less than a certain level, the certain level is an arbitrarily set reference output voltage.

   Further, preferably, when the OFD voltage in the solid-state imaging device of the present invention is set higher than the normal set voltage value by a predetermined voltage, the OFD voltage to be set higher is set as the maximum settable OFD voltage.

Further, preferably, when the electronic shutter pulse application time in the solid-state imaging device of the present invention is set longer than the normal setting time by a predetermined time, the electronic shutter pulse application time set to be longer is set to the maximum electronic shutter pulse application that can be set. Time.

   Further preferably, when the electronic shutter speed in the solid-state imaging device of the present invention is set faster than the electronic shutter speed by the normal exposure control by a predetermined speed, the electronic shutter speed to be set faster is set as the maximum electronic shutter speed that can be set. To do.

  The electronic information device of the present invention is one in which an image is taken using the solid-state imaging device of the present invention as an imaging unit, thereby achieving the above object.

  With the above configuration, the operation of the present invention will be described below.

  In the present invention, when imaging a subject with extremely high illuminance such as direct imaging of intense light such as sunlight, an imaging signal (effective video signal) corresponding to each pixel of the subject image from the effective pixel unit. When there is no level difference (output voltage) between the black level signal (OB signal from the OB section) or when it is below a certain level, the OFD voltage is set high and the photoelectric conversion element such as a photodiode is connected to the base side. By allowing the signal charge to flow through the signal converter, the signal charge excessively accumulated in the photoelectric conversion element can be quickly discharged. And / or when there is no level difference (output voltage) between the image pickup signal (effective video signal) and the black level signal (OB signal from the OB unit), or when the level difference falls below a certain level, By increasing the shutter pulse application time or increasing the electronic shutter speed so that the signal charge is discharged more quickly from the photoelectric conversion element, the signal charge accumulated excessively in the photoelectric conversion element can be quickly removed. It becomes possible to discharge.

  On the other hand, in Patent Document 1, when the electronic shutter time (exposure time) is shorter than a certain time, the output voltage of the OFD voltage setting circuit is increased by a predetermined voltage value. Is determined to determine whether the level difference between the black level (OB level) of the OB signal and the effective video signal corresponding to the subject image from the effective pixel portion is a constant level, and the output voltage is set to a constant level. Therefore, the electronic shutter time (exposure time) is adjusted to be longer or shorter. On the other hand, in the present invention, there is no level difference between the effective video signal and the OB signal, or the level difference is below a certain level, regardless of the length of the electronic shutter time (exposure time) as in Patent Document 1. In this case, since the OFD voltage and the electronic shutter operation are directly adjusted, it is possible to shorten the time from the light irradiation to the adjustment. Further, as in Patent Document 1, even if excessive light is incident, the electronic shutter time (exposure time) operates in a direction in which the electronic shutter time (exposure time) becomes longer, and the OFD voltage does not become an electronic shutter time or electronic shutter speed that controls the OFD voltage. There is no problem that is not controlled. This makes it possible to more reliably suppress image defects that occur when intense light such as sunlight is irradiated on the solid-state imaging device.

  When controlling both the OFD voltage and the electronic shutter operation, if the amount of charge generated in the photoelectric conversion element is larger than the amount of charge that can be discharged from the photoelectric conversion element by controlling the electronic shutter operation, image distortion There is a possibility that the occurrence of problems such as cannot be suppressed. Therefore, it is preferable to set the OFD voltage high before controlling the electronic shutter operation, and then increase the electronic shutter pulse application time or set the electronic shutter speed fast.

  Furthermore, even if the OFD voltage and the electronic shutter operation are adjusted, it can be determined that the image is dark when there is no level difference between the effective video signal and the OB signal or the level difference is below a certain level. . In this case, if the OFD voltage is set high, the amount of charge discharged to the substrate side is reduced to increase the amount of charge accumulated in the photoelectric conversion element, thereby increasing the effective video signal level. Is possible. In addition, the period during which charges are accumulated in the photoelectric conversion element is lengthened by setting the electronic shutter pulse application time to be shorter if the electronic shutter pulse application time is set to be longer, or to be slower if the electronic shutter speed is set to be faster. Thus, the amount of charge accumulated in the photoelectric conversion element can be increased, and the effective video signal level can be increased. When controlling both the OFD voltage and the electronic shutter operation, is the electronic shutter pulse application time set short before setting the OFD voltage low? Alternatively, it is preferable to set the electronic shutter speed slower and then set the OFD voltage lower.

  As described above, according to the present invention, even when excessive light is incident on the solid-state imaging device, there is no level difference between the imaging signal (effective video signal) and the black level signal (OB signal), or the level difference is constant. By controlling the OFD voltage and the electronic shutter operation when the level is below the level, it is possible to suppress the occurrence of image defects and obtain a good screen display.

Hereinafter, Embodiments 1 to 4 of the solid-state imaging device of the present invention and Embodiment 5 of the electronic information device of the present invention using the solid-state imaging device in an imaging unit will be described in detail with reference to the drawings.
(Embodiment 1)
FIG. 1 is a block diagram illustrating a configuration example of a main part of a solid-state imaging device according to Embodiment 1 of the present invention.

  As shown in FIG. 1, the solid-state imaging device 10 according to the first embodiment includes a CCD 1 as a solid-state imaging device capable of imaging by subjecting subject light to photoelectric conversion, and a CDS for reducing noise in an imaging signal from the CCD 1. A circuit 2, an OB clamp circuit 3 that clamps a black level signal (OB signal) and fixes it to a DC level, a clamp pulse generation circuit 4 that outputs a clamp pulse to the OB clamp circuit 3, and a gamma correction process and a white balance process It is possible to perform exposure control such as a video signal processing unit 5 that performs various video signal processing such as, a detection circuit 6 that detects an image signal and an OB signal and detects a level difference therebetween, and controls an electronic shutter speed. Image sensor driving means for performing various operations such as exposure operation, signal charge accumulation / reading operation, and charge transfer operation on the exposure control unit 7 and the CCD 1 A CCD driving circuit 8 and, and a OFD voltage setting circuit 9 which enables setting control the OFD voltage for flowing more than necessary signal charges from the CCD1 into base 11 side.

  The CCD 1 is, for example, an IT CCD, and sequentially outputs imaging signals obtained by subjecting subject image light condensed and incident through a lens (not shown) to photoelectric conversion by a plurality of light receiving units (photoelectric conversion elements).

Hereinafter, a configuration example of a main part of the CCD 1 will be described in detail with reference to FIGS. 2 (a) and 2 (b).
FIGS. 2A and 2B are block diagrams schematically showing an example of the configuration of the main part of the CCD 1 in FIG.

  As shown in FIG. 2A, the CCD 1 is provided with an effective pixel portion 12 on which light corresponding to a subject image (subject light) is incident on the base 11, as in the case of a conventional CCD. . As shown in FIG. 2B, the effective pixel section 12 includes a plurality of photodiodes 13 that are photoelectric conversion elements arranged in a two-dimensional matrix in the vertical and horizontal directions (matrix direction). An imaging signal (effective video signal) corresponding to each pixel of the subject image is output from the pixel unit 12.

  Further, as shown in FIG. 2A, an OB (optical black) portion 14 is provided in the peripheral portion of the effective pixel portion 12. A plurality of photodiodes 13 (not shown) that are photoelectric conversion elements are also arranged in the OB portion 14 in the vertical direction and the horizontal direction, and these photodiodes 13 are covered with a light shielding member such as aluminum. As a result, the light corresponding to the subject image is blocked by the OB unit 14 and is not incident on the plurality of photodiodes 13 of the OB unit 14, and the optical black level from the photodiodes 13 of the OB unit 14 is reduced. A black level signal (OB signal) used as a reference is output. In one horizontal period, as shown in FIG. 3 described later, an effective video signal period in which signal charges corresponding to each pixel of the subject image are output from the effective pixel unit 12 as an imaging signal, and the OB unit 14 And an OB period in which a black level signal (OB signal) corresponding to the black level is output.

Further, as shown in FIG. 2B, the CCD 1 includes a vertical shift register 15 provided in the vertical direction along each column of the plurality of photodiodes 13 and a horizontal line parallel to each row of the plurality of photodiodes 13. A horizontal shift register 17 that is provided in the direction and transfers the signal charge from the vertical shift register 15 to the charge detection unit (output circuit) 16 is provided.
The signal charges photoelectrically converted by each photodiode 13 and moved to the corresponding vertical shift register 15 are sequentially transferred in the direction of the horizontal shift register 17. In this example, signal charges are transferred in the vertical direction in the vertical shift register 15 by the four-phase drive signals φV1 to φV4. The signal charges transferred from the vertical shift register 15 to the horizontal shift register 17 are sequentially transferred through the horizontal shift register 17 toward the charge detection unit 16. In this example, signal charges are transferred to the horizontal shift register 17 in the horizontal direction by two-phase driving signals φH1 and φH2. In the charge detection unit 16, the transferred signal charge is detected, converted into an imaging signal, and output to the outside.

  The CDS circuit 2 receives an imaging signal (CCD output) output from the CCD 1 in one horizontal period, and removes a clock component included in the imaging signal to reduce noise.

  The OB clamp circuit 3 clamps an output signal (OB signal) from the OB section 14 of the CCD 1 input from the CDS circuit 2 when a clamp pulse is supplied from the clamp pulse generation circuit 4 during the OB period, and direct current is supplied. Fix to level. As a result, an OB level signal used as an optical black level reference is generated. The output image pickup signal (effective video signal) from the effective pixel unit 12 of the CCD 1 is output from the OB clamp circuit 3 as a video signal clamped with reference to the black level signal from the OB unit 14.

  Here, each output signal from the CCD 1, the CDS circuit 2 and the OB clamp circuit 3 will be described with reference to FIG. 3A and FIG.

  3A shows a normal operation, and FIG. 3B shows an imaging signal (effective video signal) corresponding to each pixel of the subject image output from the effective pixel unit 12 of the CCD 1 when excessive light is incident. And the CCD output output from the CCD 1 including the black level signal (OB level) corresponding to the black level output from the OB unit 14, the CDS output output from the CDS circuit 2, and the OB supplied to the video signal processing unit 6. A clamp circuit output signal (video output) is shown.

   As shown in FIGS. 3A and 3B, in one horizontal period, an effective video signal period in which an imaging signal with each screen corresponding to the subject image light is output from the effective pixel unit 12 of the CCD 1. And an OB period in which an OB signal corresponding to the black level is output from the OB unit 12.

   In the normal operation shown in FIG. 3A, the CCD output includes an imaging signal (effective video signal) corresponding to each pixel of the subject image from the effective pixel unit 12 in the effective video signal period, and the effective video signal period. A black level signal (OB signal) corresponding to the black level from the OB unit 14 is output in the OB period subsequent to OB. A signal obtained by removing the clock component from these signals is output as a CDS output from the CDS circuit 2. As an image output, an OB clamp circuit 3 outputs an image signal based on a black level signal photoelectrically converted by the CCD 1 with respect to an imaging signal photoelectrically converted by the CCD 1. In response to this, the level difference between the black level signal (OB level) from the OB unit 14 and the imaging signal (effective video signal) corresponding to each pixel of the subject image from the effective pixel unit 12 is detected from the detection circuit 6. Is output.

   On the other hand, as shown in FIG. 3B, when excessive light is incident on the CCD 1, signal charges generated in each light receiving portion (photodiode 13; photoelectric conversion element) of the effective pixel portion 12 correspond to each other. The capacity of the vertical shift register 15 exceeds the capacity of the horizontal shift register 17 during the scanning period of the horizontal shift register 17. Further, the capacity of the horizontal shift register 17 is exceeded, and the charges are overflowed to the OB portion 14 which is an area where there is no charge to be photoelectrically converted because it is originally shielded from light. As a result, the OB level output from the OB unit 14 is higher than that in the normal operation, and becomes a bright level different from the optical black level reference. The screen is dark and sunk. Further, when the electric charge overflows, the optical black level reference becomes a brighter level, so that the OB signal level (OB level) and the imaging signal corresponding to each pixel of the subject image from the effective pixel unit 12 are displayed. The level difference from (effective video signal) disappears, and the screen is displayed in a black state similar to that in the dark.

  The video signal processing unit 5 converts the imaging signal (effective video signal) from the effective pixel unit 12 into a video signal obtained by the OB clamp circuit 3 based on the black level signal (OB signal) from the OB unit 14. Various video signal processing such as gamma correction processing for display and white balance processing is performed.

  The detection circuit 6 detects the effective video signal and the OB signal with respect to the video signal (video output) from the OB clamp circuit 3 and detects a level difference between them. The detection circuit 6 may detect whether there is no level difference between the effective video signal and the OB signal, or whether the level difference between the effective video signal and the OB signal is a certain level or less. The exposure control unit 7 may detect the level difference detected by the circuit 6.

  The exposure control unit 7 outputs an exposure control signal for controlling the exposure of the CCD 1 to the CCD drive circuit 8 based on the signal output from the detection circuit 5. In addition, when a mechanical iris is provided on the front surface of the lens, an aperture control signal for controlling the aperture diameter of the mechanical iris from the exposure control unit 7 based on a signal output from the detection circuit 6. Is output. Further, the exposure control unit 7 outputs an OFD voltage control signal for controlling the OFD voltage to the OFD voltage setting circuit 9 based on the signal output from the detection circuit 6.

  When there is no level difference between the effective video signal (imaging signal) and the OB signal (black level signal) or when the level difference between the effective video signal and the OB signal is below a certain level, the exposure control unit 7 The electronic shutter pulse application time for discharging the signal charge to the 11 side is set longer than the normal setting time by a predetermined time, or the electronic shutter speed is set faster than the electronic shutter speed by the normal exposure control.

  The CCD drive circuit 8 drives the CCD 1 based on the exposure control signal output from the exposure control unit 7. In the exposure controller 7 and the CCD drive circuit 8, each operation is performed with reference to the signal level (OB level) clamped by the OB clamp circuit 3. The exposure control of the CCD 1 is controlled using, for example, an electronic shutter function provided in the CCD 1. In the CCD 1 having the electronic shutter function, an electronic shutter pulse is supplied from the CCD drive circuit 8 and a signal charge is output from the photodiode 13 in the beginning of the effective video signal period, the OB period, and the horizontal blanking period shown in FIG. Thus, the period during which signal charges are accumulated in the photodiode 13 (exposure period; electronic shutter time) is controlled.

  In the OFD voltage setting circuit 9, based on the OFD voltage control signal output from the exposure control unit 7, a malfunction such as blooming does not occur in a normal subject in the CCD 1, and a sufficient saturation level can be secured. The OFD voltage for discharging excessive charges is adjusted to a proper voltage.

  In the OFD voltage setting circuit 9, when there is no level difference between the effective video signal and the OB signal or when the level difference between the effective video signal and the OB signal is below a certain level, more signal charges than necessary are transferred from the CCD 1 to the base 11 side. The OFD voltage for flowing in is set higher than the normal set voltage by a predetermined voltage.

  Hereinafter, the function of the OFD voltage in the photodiode 13 provided for each pixel of the CCD 1 will be described in detail with reference to FIG.

  FIG. 4 is a schematic diagram for explaining an overcharge discharging function of the OFD voltage in the photodiode 13 of FIG.

  As shown on the left side of FIG. 4, the photodiode 13a includes a potential wall 21 provided between adjacent vertical shift registers (not shown) and excessive signal charges photoelectrically converted by the photodiode 13a. A potential hole 22a for discharging 20a to the base 11 side is provided.

  The potential wall 21 is a partition wall provided so that the signal charge 20a photoelectrically converted by the photodiode 13a does not flow into the adjacent vertical shift register.

  If there is too much signal charge 20a photoelectrically converted by the photodiode 13a, the signal charge 20a flows over the wall 21 to the adjacent vertical shift register, causing problems such as blooming. In order to avoid this problem, an excessive charge discharging hole 22a is provided at a height with a wall so that an excessive signal charge 20a flows to the base 11 side of the CCD 1.

  The excess charge discharging hole 22a is an overflow drain (OFD), and the height of the excess charge discharging hole 22a, that is, accumulated in the photodiode 13a is changed by changing the OFD voltage for discharging the excess charge. The amount of charge that is generated can be appropriately limited.

  As shown in the right side of FIG. 4, when the OFD voltage is increased, the height of the excess charge discharging hole 22b is decreased, and the signal charge 20b accumulated in the photodiode 13b is decreased. As a result, even when intense light is irradiated, the signal charge 20b does not overflow into the adjacent vertical shift register (not shown).

  This OFD voltage is appropriately adjusted to a voltage that does not cause a problem such as blooming in a normal subject and can sufficiently secure a saturation level.

  As described with reference to FIG. 3B, intense light such as sunlight is applied to the photodiode 13, and the photoelectrically converted signal charge is applied to each capacitance such as the photodiode capacitance, particularly the horizontal shift register 17. When the horizontal transfer capacity is exceeded, when the horizontal clamping is performed by the level difference between the effective video signal from the effective pixel unit 12 in the horizontal shift register 17 and the OB signal from the OB unit 14, the effective pixel unit 12 and the OB unit The signal charge overflows in both of them, and the level difference between the effective video signal from the effective pixel unit 12 and the OB signal from the OB unit 14 disappears, or the level difference falls below a certain level.

  In the detection circuit 6, there is no signal level difference between the effective video signal from the effective pixel unit 12 and the OB signal from the OB unit 14. Judged to be in a state. For this reason, in order to increase the amount of incident light from the detection circuit 6, the electronic shutter time (exposure time) is increased or the electronic shutter speed is decreased with respect to the exposure control unit 7 and the CCD drive circuit 8. Thus, the control signal is output so as not to perform the shutter operation as much as possible.

  Therefore, in the first embodiment, there is no signal level difference between the effective video signal from the effective pixel unit 12 and the OB signal from the OB unit 14, or the level difference is equal to or lower than a certain level, and the dark level is low. The exposure control unit 7 so as to increase the OFD voltage with respect to the OFD voltage setting circuit 9 when it is impossible to determine whether or not the above-described malfunction occurs due to excessive light being incident. The OFD voltage control signal is output from. The OFD voltage setting circuit 9 receives this OFD voltage control signal and generates an OFD voltage that is higher than the normal time by a predetermined voltage value at the OFD terminal of the CCD 1.

  As described above, according to the first embodiment, when intense light such as sunlight is incident, even if the signal charge subjected to photoelectric conversion exceeds each capacitance such as a photodiode capacitance and the entire screen becomes black, OFD By setting the voltage higher than normal, setting the electronic shutter pulse application time longer than normal, or increasing the electronic shutter speed faster than normal, more charges than necessary from the photodiode 13 to the substrate 11 side. Since the signal charge accumulated in the photodiode 13 can be reduced by discharging (a charge amount exceeding the set charge amount), it is possible to prevent the occurrence of problems such as image disturbance.

The first embodiment will be further described. When there is no level difference between the effective video signal and the OB signal, or when the level difference between the effective video signal and the OB signal is below a certain level, the OFD voltage setting circuit 9 first increases the normal OFD voltage by a predetermined voltage. Then, it is preferable that the exposure control unit 7 sets the normal electronic shutter application time longer by a predetermined time, or sets the normal electronic shutter speed faster by a predetermined speed. This is because, when controlling both the OFD voltage and the electronic shutter operation, the amount of charge generated in the CCD 1 is larger than the amount of charge that can be discharged from the CCD 1 to the substrate 11 side by controlling the electronic shutter operation. This is because the occurrence of problems such as image disturbance may not be suppressed.
(Embodiment 2)
In the first embodiment, the solid-state imaging device 10 includes an effective pixel unit 12 in which a plurality of photodiodes 13 capable of photoelectrically converting incident light are arranged and an imaging signal corresponding to each pixel of the subject image is output as an effective video signal. Further, the CCD 1 having an OB section 14 in which a plurality of photodiodes 13 covered with a light shielding member are arranged and used as an optical black level reference is output as an OB signal, and the effective pixel section 12. The video signal processing unit 5 that performs various signal processing on the effective video signal based on the OB signal from the OB unit 14, and there is no level difference between the effective video signal and the OB signal, or OF for flowing a signal charge more than a preset necessary value from the CCD 1 to the substrate 11 when the level difference of the OB level signal is below a certain level. When there is no level difference between the effective video signal and the OB signal, or when the level difference between the effective video signal and the OB signal is below a certain level, the signal charge from the CCD 1 is set. Set the electronic shutter pulse application time to be output longer than the normal setting time, or set the electronic shutter speed faster than the normal setting speed (set the electronic shutter time shorter than the normal setting time). Although an example in which the exposure control unit 7 is provided has been described, in the second embodiment, only the exposure control by the exposure control unit 7 is used without using the OFD voltage setting control by the OFD voltage setting circuit 9 of the first embodiment. The case where is used will be described.

  FIG. 5 is a block diagram illustrating a configuration example of a main part of a solid-state imaging device according to Embodiment 2 of the present invention. In addition, the same code | symbol is attached | subjected and demonstrated to the member which show | plays the same effect as the structural member of FIG.

  As shown in FIG. 5, the solid-state imaging device 10 </ b> A according to the second embodiment includes a CCD 1 as a solid-state imaging element that can capture an image by subjecting subject light to photoelectric conversion, and a CDS circuit 2 that reduces noise in an imaging signal from the CCD 1. An OB clamp circuit 3 that clamps the OB signal and fixes it to a DC level, a clamp pulse generation circuit 4 that outputs a clamp pulse to the OB clamp circuit 3, a video signal processor 5 that performs various signal processing, and an effective video A detection circuit 6 that detects a level difference between the signal (imaging signal) and the OB signal and exposure control such as controlling the electronic shutter speed is enabled, and there is a level difference between the effective video signal and the OB signal. Or when an electronic shutter pulse is applied to output signal charges from the CCD 1 when the level difference between the effective video signal and the OB signal is below a certain level. The has or longer, or an exposure control unit 7A that sets fast electronic shutter speed, and a CCD driving circuit 8 as an image pickup device driving means.

  In the solid-state imaging device 10A according to the second embodiment, there is no signal level difference between the effective video signal from the effective pixel unit 12 and the OB signal from the OB unit 14, or the level difference is a certain level or less. When it is dark or when it is impossible to determine whether excessive light is incident and the above-described problem has occurred, whether or not this condition is met is detected by the detection circuit 6 or exposure. In response to detection by the control unit 7A, the exposure control unit 7A makes the electronic shutter pulse application time longer than the normal setting time, or makes the electronic shutter speed faster than the normal setting speed. The control signal is output to the CCD drive circuit 8. In response to this control signal, the CCD drive circuit 8 generates a drive signal for extending the electronic shutter pulse application time so that the CCD 1 performs more shutter operations than during normal control.

As described above, according to the second embodiment, when intense light such as sunlight is incident, even when the signal charge subjected to photoelectric conversion exceeds each capacitance such as a photodiode capacitance and the entire screen becomes black, By making the electronic shutter pulse application time longer or making the electronic shutter speed faster, it is possible to quickly discharge more charges than necessary from the photodiode 13, thereby preventing the occurrence of problems such as image distortion. Can do.
(Embodiment 3)
In the first embodiment, the solid-state imaging device 10 includes an effective pixel unit 12 in which a plurality of photodiodes 13 capable of photoelectrically converting incident light are arranged and an imaging signal corresponding to each pixel of the subject image is output as an effective video signal. Further, the CCD 1 having an OB section 14 in which a plurality of photodiodes 13 covered with a light shielding member are arranged and used as an optical black level reference is output as an OB signal, and the effective pixel section 12. The video signal processing unit 5 that performs various signal processing on the effective video signal based on the OB signal from the OB unit 14, and there is no level difference between the effective video signal and the OB signal, or OF for flowing a signal charge more than a preset necessary value from the CCD 1 to the substrate 11 when the level difference of the OB level signal is below a certain level. When there is no level difference between the effective video signal and the OB signal, or when the level difference between the effective video signal and the OB signal is below a certain level, the signal charge from the CCD 1 is set. Set the electronic shutter pulse application time to be output longer than the normal setting time, or set the electronic shutter speed faster than the normal setting speed (set the electronic shutter time shorter than the normal setting time). Although an example of the case where the exposure control unit 7 is provided has been described, in the third embodiment, only the OFD voltage setting control by the OFD voltage setting circuit 9 is performed without using the control by the exposure control unit 7 of the first embodiment. The case of using will be described.

  FIG. 6 is a block diagram illustrating an exemplary main configuration of a solid-state imaging device according to Embodiment 3 of the present invention. In addition, the same code | symbol is attached | subjected and demonstrated to the member which show | plays the same effect as the structural member of FIG.

  As shown in FIG. 6, the solid-state imaging device 10B according to the third embodiment includes a CCD 1 as a solid-state imaging device that can perform imaging by subjecting subject light to photoelectric conversion, and a CDS circuit 2 that reduces noise in an imaging signal from the CCD 1. An OB clamp circuit 3 that clamps the OB signal and fixes it to a DC level, a clamp pulse generation circuit 4 that outputs a clamp pulse to the OB clamp circuit 3, a video signal processor 5 that performs various signal processing, and an effective video As a detection circuit 6 that detects a signal (imaging signal) and an OB signal and detects a level difference between them, an exposure control unit 7B that performs normal exposure control such as controlling an electronic shutter speed, and an imaging element driving unit When there is no level difference between the effective video signal and the OB signal and the level difference between the effective video signal and the OB signal is below a certain level, The OFD voltage for flowing a main or more signal charges from the photoelectric conversion element to the base 11 side than the normal set voltage value and a OFD voltage setting circuit 9B to set higher by a predetermined value.

  In the solid-state imaging device 10B of the third embodiment, there is no signal level difference between the effective video signal from the effective pixel unit 12 and the OB signal from the OB unit 14, or the level difference is not more than a certain level. When it is dark or when it is impossible to determine whether excessive light is incident to cause the above-described problem, the detection circuit 6 detects whether this condition is satisfied and the OFD is detected. A control signal is output from the detection circuit 6B to the OFD voltage setting circuit 9B so that the OFD voltage is made higher than normal during the voltage setting circuit 9B. The OFD voltage setting circuit 9B receives this control signal and generates an OFD voltage higher than a predetermined voltage value at the normal time at the OFD terminal of the CCD 1.

As described above, according to the third embodiment, even when intense light such as sunlight is incident, even when the photoelectrically converted signal charge exceeds each capacitance such as a photodiode capacitance and the entire screen becomes black, By controlling the OFD voltage higher, it is possible to prevent the occurrence of problems such as image disturbance.
(Embodiment 4)
In the fourth embodiment, in the first embodiment, the OFD voltage setting circuit 9 sets the normal OFD voltage higher by a predetermined voltage, and the exposure control unit 7 sets the electronic shutter application time longer by a predetermined time, or In a dark state when the electronic shutter speed is set faster by a predetermined speed and there is no level difference between the effective video signal and the OB signal, or the level difference between the effective video signal and the OB signal is a certain level or less. If it is determined that the electronic shutter is applied, the exposure control unit 7 sets the electronic shutter application time during normal control to be shorter by a predetermined time, or sets the electronic shutter speed during normal control to be lower by a predetermined speed, and then the OFD voltage setting circuit. 9, the case where the OFD voltage during normal control is set lower by a predetermined voltage will be described.

  In this case, when there is no level difference between the effective video signal and the OB signal or the level difference between the effective video signal and the OB signal is equal to or lower than a certain level, the OFD voltage setting circuit 9 first sets the normal OFD voltage. Alternatively, the exposure control unit 7 may set the normal electronic shutter application time longer by a predetermined time, or the normal electronic shutter speed may be set higher by a predetermined speed.

  That is, in the solid-state imaging device according to the fourth embodiment, when intense light such as sunlight is incident, the excessive charge photoelectrically converted is extremely large and can be discharged from the photodiode 13 to the substrate 11 side by the electronic shutter operation. When the amount of charge generated by photoelectric conversion by the photodiode 13 is larger than the amount of charge, there is a possibility that the occurrence of problems such as image disturbance cannot be suppressed. Therefore, before the exposure control unit 7 and the CCD drive circuit 8 in FIG. 1 perform the electronic shutter operation, the OFD voltage setting circuit 9 causes the CCD 1 to set an OFD voltage higher than that in the normal control to set the image. Occurrence of problems such as disturbance can be efficiently prevented.

In the solid-state imaging device according to the fourth embodiment, the OFD voltage setting circuit 9 sets the OFD voltage during normal control higher, and the exposure control unit 7 and the CCD drive circuit 8 extend the electronic shutter pulse application time during normal control. Even if it is set or the electronic shutter speed during normal control is set faster, there is no level difference between the effective video signal and the OB signal, or the level difference between the effective video signal and the OB signal is below a certain level. Can be determined to be dark. In this case, before the OFD voltage setting circuit 9 lowers the voltage to a level lower than the OFD voltage during normal control, the exposure control unit 7 and the CCD drive circuit 8 shorten the electronic shutter pulse application time during normal control, or Then, it is slower than the electronic shutter speed at the time of normal control, and thereafter, the OFD voltage setting circuit 9 sets the OFD voltage to be lower than the OFD voltage at the time of normal control.
(Embodiment 5)
In the fifth embodiment, electronic information devices such as various cameras that perform image shooting using the solid-state imaging device of the first to fourth embodiments as an imaging unit will be described.

  FIG. 7 is a block diagram illustrating a configuration example of a main part of an electronic information device according to the fifth embodiment of the present invention.

  In FIG. 7, an electronic information device 30 according to the fifth embodiment is a surveillance camera, a door phone camera, an in-vehicle camera, a video phone camera, a mobile phone camera, or the like, and is described in any of the first to fourth embodiments. A solid-state imaging device, a display unit 31 on which an image of an object captured by the solid-state imaging device and an operation screen are displayed, and a memory 32 for storing the image of the subject imaged by the solid-state imaging device 10 And an operation unit 33 for a user of the electronic information device 30 to input an instruction.

  According to the electronic information device 30 of the fifth embodiment, since image capturing is performed using the solid-state imaging device described in any of the first to fourth embodiments, when intense light such as sunlight is incident. However, even when the photoelectrically converted signal charge exceeds each capacitance such as photodiode capacitance and the entire screen becomes black, by controlling the OFD voltage and the electronic shutter operation, it is possible to prevent the occurrence of problems such as image distortion. A good captured image can be obtained.

  As described above, according to the first to fourth embodiments, when an object with extremely high illuminance such as direct imaging of intense light such as sunlight is captured, a signal corresponding to the subject image from the effective pixel unit (effective video) Signal) and the OB signal from the OB section is detected, and if there is no level difference, or this level difference is below a certain level, the OFD voltage setting circuit 9 sets the OFD voltage higher. Thus, the amount of charge accumulated in the photodiode 13 can be reduced. Further, the exposure control unit 7 can further extend the electronic shutter pulse application time or increase the electronic shutter speed to discharge more signal charges from the photodiode 13. Thereby, even when intense light such as sunlight is irradiated, it is possible to suppress the occurrence of an image defect. The solid-state imaging device described in any one of the first to fourth embodiments is the same as that of the electronic information device of the fifth embodiment such as a monitoring camera, a door phone camera, an in-vehicle camera, a television phone camera, and a mobile phone camera. It can be used for the imaging unit, and it is possible to prevent the occurrence of problems such as image disturbance and obtain a good captured image.

  Although not particularly described in the first to fourth embodiments, the “constant level” when the level difference between the effective video signal and the OB signal is equal to or less than a certain level is an arbitrarily set reference output voltage. Further, when the OFD voltage is set higher than the normal set voltage value by a predetermined voltage, it is preferable that the OFD voltage to be set higher is the maximum settable OFD voltage. Further, when the electronic shutter application time is set longer than the normal setting time by a predetermined time, it is preferable that the electronic shutter application time set to be longer is set to the maximum electronic shutter application time that can be set. Further, when the electronic shutter speed is set faster than the electronic shutter speed by the normal exposure control by a predetermined speed, it is preferable to set the electronic shutter speed to be set to the maximum electronic shutter speed that can be set.

  Here, the detection circuit 6 detects whether there is no level difference between the imaging signal and the black level signal, or whether the level difference between the imaging signal and the black level signal is equal to or lower than a certain level. “Constant level” when the difference is below a certain level, “Predetermined voltage” when “OFD voltage is set higher than the normal setting voltage value by a predetermined voltage”, and “Electronic shutter application time set longer than the normal setting time by a predetermined time” The “predetermined time” and “predetermined speed” of “set the electronic shutter speed faster by a predetermined speed than the electronic shutter speed by the normal exposure control” will be described.

  The “constant level” is a reference output voltage arbitrarily set by a level difference (output voltage) between the imaging signal and the black level signal. This controls the electronic shutter operation / OFD voltage to keep the output voltage at the reference output voltage.

  For example, when the level difference (output voltage) between the imaging signal and the black level signal = 700 mV is set as the reference output voltage, the output voltage = 700 mV or less → the electronic shutter operation is OFF, and the OFD voltage is a normally set voltage. In this case, the shutter speed varies so that the output voltage becomes a constant level.

  Level difference (output voltage) between imaging signal and black level signal = 750 mV → electronic shutter operation ON (for example, 1/100 second shutter), output voltage = 1500 mV → electronic shutter operation ON (for example, 1/10000 second shutter) . The OFD voltage is normally set voltage + predetermined voltage. In this case, the reference output voltage value varies depending on each camera system.

  The “predetermined voltage” is a voltage that is normally set voltage + predetermined voltage and is not less than the minimum voltage required to solve this problem and not more than the absolute maximum rating of the solid-state imaging device. The “predetermined voltage” is suitably 0.5 to 5.0 V, for example.

  The “predetermined time” is an electronic shutter pulse application time for discharging signal charges from the photoelectric conversion unit (photodiode unit) to the substrate side, and is the minimum time required to solve this problem. The “predetermined time” varies depending on each camera system. For example, 6.7 milliseconds is appropriate for a 1/100 second shutter.

  The above “predetermined speed” refers to the time from the last electronic shutter pulse that discharges signal charges from the photoelectric conversion element to the substrate side until the readout time for reading from the photoelectric conversion unit (photodiode unit) to the vertical transfer unit ends. It is the speed corresponding to the time, and the speed corresponding to the minimum time required to solve this problem. This also differs depending on each camera system as in the case of the “predetermined time”. However, for example, 10 msec is appropriate for a 1/100 second shutter.

  In the first to fourth embodiments, the maximum OFD voltage and the maximum electronic shutter speed described above are not particularly described. However, the maximum OFD voltage is a voltage that is equal to or lower than the absolute maximum rating of the solid-state imaging device, and the maximum electronic shutter speed. Is a speed corresponding to the time required to read out charges from the photodiode portion to the vertical transfer portion. In this case, the read pulse time varies depending on each solid-state imaging device.

  In the fifth embodiment, a monitoring camera, a door phone camera, an in-vehicle camera, a television phone camera, a mobile phone camera, or the like using the solid-state imaging device described in any of the first to fourth embodiments as an imaging unit. Although the electronic information device has been described, the present invention is not limited to this, and for example, electronic information having a digital camera such as a digital video camera and a digital still camera, and an image input device such as an image input camera, a scanner, a facsimile, and a camera-equipped mobile phone device It may be a device. The electronic information device in this case is a recording medium that records data after performing predetermined signal processing for recording high-quality image data obtained by using the solid-state imaging device according to any of the first to fourth embodiments of the present invention as an imaging unit. A memory unit, a display means such as a liquid crystal display device for displaying the image data on a display screen such as a liquid crystal display screen after predetermined signal processing for display, and predetermined signal processing for communication of the image data. After that, at least one of a communication unit such as a transmission / reception device for performing communication processing and an image output unit for printing (printing) and outputting (printing out) the image data is provided.

  As mentioned above, although this invention has been illustrated using preferable Embodiment 1-5 of this invention, this invention should not be limited and limited to this Embodiment 1-5. It is understood that the scope of the present invention should be construed only by the claims. It is understood that those skilled in the art can implement an equivalent range based on the description of the present invention and the common general technical knowledge from the description of specific preferred embodiments 1 to 5 of the present invention. Patents, patent applications, and documents cited herein should be incorporated by reference in their entirety, as if the contents themselves were specifically described herein. Understood.

  The present invention uses a solid-state imaging device that is capable of performing exposure control by the EE system and photoelectrically converts incident light (subject light) by each light-receiving unit (each pixel unit), and uses the solid-state imaging device as an imaging unit. In the field of electronic information equipment such as surveillance cameras, door phone cameras, in-vehicle cameras, TV phone cameras, and mobile phone cameras where images are captured, even if excessive light is incident on a solid-state image sensor, the imaging signal ( When there is no level difference between the effective video signal) and the black level signal (OB signal) or the level difference is equal to or less than a certain level, an image defect occurs by controlling the OFD voltage and the electronic shutter operation. This can be suppressed and a good screen display can be obtained. Such a solid-state imaging device can be used for an imaging unit of an electronic information device such as a monitoring camera, a door phone camera, a corporate bond camera, a television phone camera, or a mobile phone camera.

It is a block diagram which shows the principal part structural example of the solid-state imaging device which concerns on Embodiment 1 of this invention. (A) And (b) is a schematic diagram for demonstrating the CCD structure in the solid-state imaging device of FIG. (A) shows the normal operation, and (b) shows the signal corresponding to the subject image output from the effective pixel portion of the CCD (effective video signal) and the black level output from the OB portion when excessive light is incident. Signal waveform diagram of signal (CCD output) output from CCD including corresponding signal (OB level), signal output from CDS circuit (CDS output), signal supplied to video signal processing unit (video signal output) It is. It is a schematic diagram for demonstrating the function of OFD voltage in the photodiode of FIG.2 (b). It is a block diagram which shows the principal part structural example of the solid-state imaging device which concerns on Embodiment 2 of this invention. It is a block diagram which shows the principal part structural example of the solid-state imaging device which concerns on Embodiment 3 of this invention. It is a block diagram which shows the principal part structural example of the electronic information equipment which concerns on Embodiment 5 of this invention.

Explanation of symbols

1 CCD
2 CDS circuit 3 OB clamp circuit 4 clamp pulse generation circuit 5 video signal processing unit 6 detection circuit 7, 7A, 7B exposure control unit 8 CCD drive circuit 9, 9B OFD voltage setting circuit 10, 10A, 10B solid-state imaging device 11 base 12 Effective pixel portion 13, 13a, 13b Photodiode 14 OB portion 15 Vertical shift register 16 Charge detection portion 17 Horizontal shift register 20a, 20b Charge accumulated in photodiode 21 Potential wall 22a, 22b Hole for discharging charge

Claims (20)

In a solid-state imaging device that obtains a video signal based on a black level signal photoelectrically converted by the solid-state imaging device, with respect to an imaging signal photoelectrically converted by a solid-state imaging device provided on a base,
Based on the imaging signal and the black level signal, whether there is no level difference between the imaging signal and the black level signal, or whether the level difference between the imaging signal and the black level signal is a certain level or less. A determination circuit for determining;
When the determination result of the determination circuit indicates that there is no level difference between the image pickup signal and the black level signal, or the level difference between the image pickup signal and the black level signal is equal to or less than a certain level, an unnecessary signal An OFD voltage setting circuit for setting an OFD (overflow drain) voltage for causing an electric charge to flow from the photoelectric conversion element of the solid-state imaging device to the base side by a predetermined voltage higher than the normal setting voltage;
When the determination result of the determination circuit is that there is no level difference between the imaging signal and the black level signal, or the level difference between the imaging signal and the black level signal is equal to or less than a certain level, the photoelectric conversion element Exposure control that sets the electronic shutter pulse application time for discharging the signal charge to the side longer by a predetermined time than the normal setting time, or sets the electronic shutter speed by a predetermined speed higher than the electronic shutter speed by the normal exposure control A solid-state imaging device. In a solid-state imaging device that obtains a video signal based on a black level signal photoelectrically converted by the solid-state imaging device, with respect to an imaging signal photoelectrically converted by a solid-state imaging device provided on a base,
Based on the imaging signal and the black level signal, whether there is no level difference between the imaging signal and the black level signal, or whether the level difference between the imaging signal and the black level signal is a certain level or less. A determination circuit for determining;
When the determination result of the determination circuit indicates that there is no level difference between the imaging signal and the black level signal or the level difference between the imaging signal and the black level signal is equal to or less than a certain level, the solid-state imaging device The electronic shutter pulse application time for discharging the signal charge from the photoelectric conversion element to the substrate side is set longer than the normal setting time by a predetermined time, or the electronic shutter speed is set higher than the electronic shutter speed by the normal exposure control. A solid-state imaging device including an exposure control unit that sets the speed faster. In a solid-state imaging device that obtains a video signal based on a black level signal photoelectrically converted by the solid-state imaging device, with respect to an imaging signal photoelectrically converted by a solid-state imaging device provided on a base,
Based on the imaging signal and the black level signal, whether there is no level difference between the imaging signal and the black level signal, or whether the level difference between the imaging signal and the black level signal is a certain level or less. A determination circuit for determining;
When the determination result of the determination circuit indicates that there is no level difference between the image pickup signal and the black level signal, or the level difference between the image pickup signal and the black level signal is equal to or less than a certain level, an unnecessary signal A solid-state image pickup device including an OFD voltage setting circuit that sets an OFD voltage for flowing an electric charge from the photoelectric conversion element of the solid-state image pickup element to the substrate side by a predetermined voltage higher than the normal setting voltage. In a solid-state imaging device that obtains a video signal based on a black level signal photoelectrically converted by the solid-state imaging device, with respect to an imaging signal photoelectrically converted by a solid-state imaging device provided on a base,
Based on the imaging signal and the black level signal, whether there is no level difference between the imaging signal and the black level signal, or whether the level difference between the imaging signal and the black level signal is a certain level or less. A determination circuit for determining;
When the determination result of the determination circuit indicates that there is no level difference between the image pickup signal and the black level signal, or the level difference between the image pickup signal and the black level signal is equal to or less than a certain level, an unnecessary signal An OFD voltage setting circuit for setting an OFD (overflow drain) voltage for causing an electric charge to flow from the photoelectric conversion element of the solid-state imaging device to the base side by a predetermined voltage higher than the normal setting voltage;
When the determination result of the determination circuit is that there is no level difference between the imaging signal and the black level signal, or the level difference between the imaging signal and the black level signal is equal to or less than a certain level, the photoelectric conversion element Exposure control that sets the electronic shutter pulse application time for discharging the signal charge to the side longer by a predetermined time than the normal setting time, or sets the electronic shutter speed by a predetermined speed higher than the electronic shutter speed by the normal exposure control With
To indicate that the determination result of said determination circuit or no level difference in the image signal and the black level signal is level difference of the image pickup signal and said black level signal is below a certain level, first the OFD the OFD voltage set higher by the predetermined voltage by the voltage setting circuit, then or the electronic shutter pulse application time by the exposure control unit sets longer by the predetermined time, the electronic shutter speed by the predetermined speed faster set solid-state image sensor you. The OFD voltage setting circuit sets the OFD voltage higher by the predetermined voltage, and the exposure control unit sets the electronic shutter pulse application time longer by the predetermined time, or increases the electronic shutter speed by the predetermined speed. In the set state, the determination result of the determination circuit further indicates that there is no level difference between the imaging signal and the black level signal, or the level difference between the imaging signal and the black level signal is equal to or less than a certain level. In this case, it is determined that the time is dark, and the exposure control unit sets the electronic shutter pulse application time shorter by a predetermined time or sets the electronic shutter speed slower by a predetermined speed, and then sets the OFD voltage. The solid-state imaging device according to claim 4 , wherein the OFD voltage is set lower by a predetermined voltage by a setting circuit. In a solid-state imaging device that obtains a video signal based on a black level signal photoelectrically converted by the solid-state imaging device, with respect to an imaging signal photoelectrically converted by a solid-state imaging device provided on a base,
Based on the imaging signal and the black level signal, whether there is no level difference between the imaging signal and the black level signal, or whether the level difference between the imaging signal and the black level signal is a certain level or less. A determination circuit for determining;
When the determination result of the determination circuit indicates that there is no level difference between the image pickup signal and the black level signal, or the level difference between the image pickup signal and the black level signal is equal to or less than a certain level, an unnecessary signal An OFD voltage setting circuit for setting an OFD (overflow drain) voltage for causing an electric charge to flow from the photoelectric conversion element of the solid-state imaging device to the base side by a predetermined voltage higher than the normal setting voltage;
When the determination result of the determination circuit is that there is no level difference between the imaging signal and the black level signal, or the level difference between the imaging signal and the black level signal is equal to or less than a certain level, the photoelectric conversion element Exposure control that sets the electronic shutter pulse application time for discharging the signal charge to the side longer by a predetermined time than the normal setting time, or sets the electronic shutter speed by a predetermined speed higher than the electronic shutter speed by the normal exposure control With
The OFD the OFD voltage set higher by the predetermined voltage by the voltage setting circuit, or the electronic shutter pulse application time by the exposure control unit sets longer by the predetermined time, faster the electronic shutter speed by the predetermined speed in the set state, further, it indicates that the judgment result of the judging circuit or no level difference in the image signal and the black level signal is level difference of the image pickup signal and said black level signal is below a certain level In this case, it is determined that the time is dark, and the exposure control unit sets the electronic shutter pulse application time shorter by a predetermined time or sets the electronic shutter speed slower by a predetermined speed, and then sets the OFD voltage. solid-state image pickup device by the setting circuit to set low the OFD voltage by a predetermined voltage.   The solid-state imaging device includes an effective pixel portion in which a plurality of the photoelectric conversion elements are arranged and each imaging signal corresponding to each pixel of the subject image is output as an effective video signal, and a photoelectric conversion element covered with a light shielding member 3. The solid-state imaging device according to claim 1, further comprising: an OB (optical black) unit that outputs a plurality of the black level signals that are arranged and used as an optical black level reference. 4. The solid-state imaging device includes: a vertical transfer unit that transfers signal charges read from the photoelectric conversion device in a vertical direction; a horizontal transfer unit that transfers signal charges from the vertical transfer unit in a horizontal direction; and the solid-state imaging device according to any one of claims 1 to 3 and 7 further comprising a charge detection unit for outputting a signal charge from the horizontal transfer unit as an image pickup signal. The solid-state image processing apparatus according to claim 7 , further comprising a video signal processing unit that performs various signal processing for display on a video signal obtained based on a black level signal from the OB unit with respect to an effective video signal from the effective pixel unit. Imaging device. The solid-state imaging according to claim 7 , further comprising: a detection circuit that detects the effective video signal and the black level signal and detects a level difference therebetween, and the detection circuit also serves as a part of the determination circuit. apparatus. The determination circuit is the detection circuit, and the detection circuit has no level difference between the imaging signal and the black level signal, or whether the level difference between the imaging signal and the black level signal is a certain level or less. The solid-state imaging device according to claim 10 which detects whether or not. The exposure control unit also serves as a part of the determination circuit, and when the level difference is detected by the detection circuit, the exposure control unit has no level difference between the imaging signal and the black level signal. The solid-state imaging device according to claim 10 , wherein it is detected whether or not a level difference between the imaging signal and the black level signal is a certain level or less.   A mechanical iris that can control the amount of light incident on the solid-state imaging device by changing the aperture diameter, and the exposure control unit determines the aperture diameter of the mechanical iris based on the black level signal. The solid-state imaging device according to claim 1, which is controlled.   4. The solid-state imaging device according to claim 1, wherein the OFD voltage is controlled by the OFD voltage setting circuit from a time when power is turned on.   The solid-state imaging device according to claim 1, wherein an electronic shutter operation is controlled by the exposure control unit from the time of power-on. If the level difference is below a certain level, the predetermined level is a solid-state imaging device according to claim 1 which is arbitrarily set reference output voltage 6, 1 1 and 1 2.   4. The solid-state imaging device according to claim 1, wherein when the OFD voltage is set higher than a normal setting voltage value by a predetermined voltage, the OFD voltage to be set higher is set as a maximum settable OFD voltage.   3. The electronic shutter pulse application time according to claim 1, wherein when the electronic shutter pulse application time is set longer than a normal set time by a predetermined time, the electronic shutter pulse application time set to be longer is set as a settable maximum electronic shutter pulse application time. Solid-state imaging device.   3. The solid-state imaging according to claim 1, wherein when the electronic shutter speed is set faster than the electronic shutter speed by the normal exposure control by a predetermined speed, the electronic shutter speed to be set faster is a settable maximum electronic shutter speed. apparatus. Electronic information device image capturing is performed using a solid-state imaging device according to claim 1 1 9 using the imaging unit.

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