JP4991415B2 - Imaging device - Google Patents

Description

The present invention relates to an imaging equipment for reading pixel signals from the solid-state imaging device.

  In recent years, many digital cameras for obtaining still images or moving images using an image sensor such as a CCD have been developed. Under such circumstances, in a solid-state imaging device such as a CCD, the number of pixels is increasing year by year, and therefore, the time required to read one still image tends to increase.

  An increase in the time required for reading is a problem directly related to a decrease in the continuous shooting speed. Further, since the dark current component increases with time, the dark current also increases with the increase of the time required for reading, and the SN of the image tends to deteriorate. For this reason, shortening the readout time is one of the high priority characteristics required for digital cameras.

The measures to shorten the read time, have been proposed those such speed and multi-line reading of the horizontal transfer clock. However, in the former, concerns about unnecessary radiation and the like increase by handling a high-speed clock, and further, since high-speed clocking tends to make horizontal transfer difficult, problems such as transfer defects are likely to occur. In the latter case, since the structure is complicated, the image pickup device itself is expensive, and there is a possibility that the image quality may be adversely affected because there are signal level offsets and noise differences in each of a plurality of different transfer paths. There is. For this reason, the hurdle to realization is high. Therefore, ideally, it is desired to reduce the readout time by a method other than both measures. Therefore, for example, Patent Document 1 discloses a method for newly reducing the readout time.

  FIG. 7 is a timing chart showing a signal charge readout method in which a conventional measure for shortening the readout time is not performed. In the figure, H1 and H2 represent horizontal transfer pulses. V1 to V4 represent four-phase vertical transfer pulses. In this reading method, a vertical line shift of signal charges is performed by a four-phase vertical transfer pulse in a so-called horizontal blanking period in which no horizontal transfer is performed.

  FIG. 8 is a timing chart showing a signal charge readout method in which measures for shortening the readout time are taken. In the figure, H1 and H2 represent horizontal transfer pulses. V1 to V4 represent four-phase vertical transfer pulses. BS represents a transfer pulse applied to a buffer storage cell (BS cell) which is located at the last stage of VCCD (vertical transfer path) and stores signal charges before HCCD (horizontal transfer path). TG represents a transfer pulse applied to a transfer gate for transferring a signal charge from the BS cell to the HCCD. In this readout method, vertical transfer of signal charges is performed by applying four-phase vertical transfer pulses in a superimposed manner during a period of horizontal transfer. In addition, only the transfer from the last stage of the vertical transfer path to the horizontal transfer path is performed during a so-called horizontal blanking period in which no horizontal transfer is performed.

  By using this readout method, the horizontal blanking period can be greatly shortened, and the time for reading out pixels for one horizontal period (1HD) and one screen will be greatly shortened. Can be improved.

Further, Patent Document 1 proposes a measure to reduce crosstalk noise when the V driver is devised, the slope of rising and falling edges of the vertical transfer pulse is changed, and vertical transfer is superimposed on horizontal transfer. .
JP 2005-269060 A

  However, in the imaging apparatus of Patent Document 1, it is possible to realize high-speed reading, but it is impossible to completely avoid the influence of crosstalk noise caused by superimposing horizontal transfer and vertical transfer.

  In addition, it has been observed that the vertical transfer pulse distorts the substrate voltage of the image sensor during the horizontal transfer period, causing fluctuations in signal output.

  Therefore, if this operation is always performed as in the image sensor of Patent Document 1, various noises become conspicuous on the screen, which may cause a practical problem.

The present invention has been made in view of the above problem, a general solid-state imaging without structure to significantly change the element, to provide a consistent imaging equipment balance of the continuous shooting speed increase and image quality With the goal.

In order to achieve the above object, an imaging apparatus of the present invention includes a plurality of photoelectric conversion elements arranged in a matrix, a vertical transfer path that vertically transfers signal charges from the photoelectric conversion elements in the vertical direction, and the vertical Supplying a solid-state imaging device having a horizontal transfer path for horizontally transferring the signal charge transferred by the transfer path in the horizontal direction, a vertical transfer pulse for driving the vertical transfer path, and a horizontal transfer pulse for driving the horizontal transfer path Driving means for driving the solid-state imaging device, amplification means for amplifying an imaging signal output from the solid-state imaging device, setting means for setting a photographing mode,
When the single-shot mode is set by the setting means, the driving means is controlled so as to drive the solid-state imaging device by a first readout method for supplying the vertical transfer pulse outside the horizontal transfer pulse supply period. and, if the gain-up amount of the amplifying means together with the continuous shooting mode is set by said setting means is larger than a predetermined value, said drive means to drive the solid-state imaging device in the first read method And when the continuous shooting mode is set by the setting means and the gain increase amount of the amplifying means is equal to or less than the predetermined value, the second transfer pulse is supplied within the horizontal transfer pulse supply period. And a control means for controlling the driving means so as to drive the solid-state imaging device by the reading method.
The imaging device of the present invention is transferred by a plurality of photoelectric conversion elements arranged in a matrix, a vertical transfer path for vertically transferring signal charges from the photoelectric conversion elements in the vertical direction, and the vertical transfer path. A solid-state imaging device having a horizontal transfer path for horizontally transferring the signal charge in the horizontal direction, a vertical transfer pulse for driving the vertical transfer path, and a horizontal transfer pulse for driving the horizontal transfer path to supply the solid-state imaging A driving means for driving the element, a temperature measuring means for measuring the temperature of the solid-state imaging device, a remaining battery level measuring means for measuring the remaining battery level, and a remaining battery level measured by the remaining battery level measuring means is predetermined. The driving means is controlled to drive the solid-state imaging device by a first readout method for supplying the vertical transfer pulse outside the horizontal transfer pulse supply period when the value is smaller than the value. When the battery remaining amount measured by the battery remaining amount measuring unit is equal to or greater than the predetermined value and the temperature measured by the temperature measuring unit is outside a predetermined range, the solid-state imaging device is used by the first reading method. When the battery remaining amount measured by the battery remaining amount measuring unit is equal to or greater than the predetermined value and the temperature measured by the temperature measuring unit is within the predetermined range. And a control means for controlling the driving means so as to drive the solid-state imaging device by a second readout method for supplying the vertical transfer pulse within the supply period of the horizontal transfer pulse. To do.

According to the onset bright, after minimal adverse effects such as cross-talk noise, it is possible to realize an improvement of the continuous shooting speed. And, the typical solid-state imaging without structure to significantly change the element, it is possible to provide a balanced image pickup apparatus of the balance of the continuous shooting speed increase and image quality.

It will be described with reference to the accompanying drawings, embodiments of the imaging equipment of the present invention. The imaging apparatus of this embodiment is applied to a digital camera that can record still images and moving images.

[First Embodiment]
FIG. 1 is a block diagram showing a schematic configuration of a digital camera according to the first embodiment. The digital camera includes an optical system 11, a mechanical shutter 13, a CCD 12, an image sensor driving device 14, a preprocess circuit 15, a digital process circuit 16, a memory 17, an LCD 18, an image conversion circuit 19, and a memory card 20. The digital camera also includes a camera control unit 21, an operation unit 22, a temperature sensor unit 23, and a battery remaining amount measurement unit 24.

  The optical system 11 includes a lens and forms a subject image on the light receiving surface of the CCD 12. The CCD 12 is a solid-state image sensor that photoelectrically converts an optical signal of a subject imaged on its light receiving surface to generate an electrical signal. Further, a mechanical shutter 13 is disposed between the optical system 11 and the CCD 12, and light incident on the CCD 12 can be blocked by closing the mechanical shutter 13.

  The image sensor driving device 14 generates a CCD driving timing pulse (CDD driving pulse) and drives the CCD 12. The output (imaging signal) of the CCD 12 driven by the image sensor driving device 14 is digitized by a pre-process circuit 15 including a sample hold (S / H), a gain amplifier, and an analog-digital conversion (A / D). It is captured by the circuit 16.

  The digital process circuit 16 performs various digital signal processing such as gamma processing and color signal processing. At this time, the digital process circuit 16 performs image signal writing / reading processing with the memory 17. The output of the digital process circuit 16 can also be displayed on the LCD display 18. The image data that has been subjected to image processing by the digital process circuit 16 is compressed via the image conversion circuit 19 and written and recorded in the memory card 20.

  The image conversion circuit 19 has a function of compressing the image data from the digital process circuit 16 and outputting it to the memory card 20, and a function of expanding the image data read from the memory card 20 and outputting it to the digital process circuit 16.

  The optical system 11, the mechanical shutter 13, the image sensor driving device 14, the preprocess circuit 15, the digital process circuit 16, the image conversion circuit 19, and the memory card 20 are each controlled by the camera control unit 21. The camera control unit 21 is connected to an operation unit 22 having functions such as release, output image size switching, continuous shooting mode / single shooting mode switching.

  The temperature sensor unit 23 (temperature measurement means) is disposed in the vicinity of the CCD 12, and the ambient temperature value is input to the camera control unit 21. The remaining battery level measurement unit 24 measures the remaining battery level, and the measured remaining level value is input to the camera control unit 21.

  In addition, the camera control unit 21 has a built-in readout method (mode) switching function (reading method switching means), which will be described later, and outputs an CCD sensor pulse corresponding to the selected readout method. 14 is controlled.

  Next, the configuration of an interline CCD, which is the CCD 12, as a solid-state imaging device used in the digital camera of this embodiment will be described. In the interline CCD, a plurality of pixels are arranged in a matrix. FIG. 2 is a diagram showing a schematic configuration of the CCD 12 as an interline CCD. The CCD 12 is mainly composed of a PD (photodiode) 1, a VCCD (vertical transfer path) 2, an HCCD (horizontal transfer path) 3, an output amplifier 4, a buffer storage cell (BS cell) 5, and a transfer gate (TG) 6. Yes.

  A PD (photodiode) 1 is a photoelectric conversion element that receives light from a subject and performs photoelectric conversion. The VCCD (vertical transfer path) 2 is a plurality of vertical shift registers for transferring the signal charge of the PD 1 in the vertical direction, and normally has a four-phase drive configuration. The HCCD (horizontal transfer path) 3 is a horizontal shift register that crosses the VCCD 2 and transfers signal charges in the horizontal direction line by line. The output amplifier 4 converts the signal charge for each pixel transferred from the HCCD 3 into a voltage signal. The buffer storage cell (BS cell) 5 temporarily stores the signal charge for one line from the VCCD 2 until it is transferred to the HCCD 3. The transfer gate (TG) 6 is provided between the buffer storage cell 5 and the HCCD 3. The HCCD 3 described above is provided at one end of the VCCD 2 and transfers the signal charge of the VCCD 2 as one row or n (positive integer) row of signal charges.

  Next, a signal reading operation in the digital camera having the above configuration will be described. First, a first reading method (first reading mode) in the digital camera of the present embodiment will be described with reference to FIG. FIG. 3 is a timing chart showing a first reading method for performing vertical transfer outside the horizontal transfer period of signal charges. The charge of PD1 is read to VCCD2 (not shown) in the column to which the charge read pulse is applied.

  In one horizontal period, the signal charges accumulated in the buffer storage cell 5 are transferred to the HCCD 3 through the transfer gate 6 in the period from t1 to t2. Thereafter, the signal charges are sequentially transferred (vertical line shift) in the direction of HCCD 3 by the four-phase drive pulses φV 1 to φV 4 applied to the transfer electrodes V 1 to V 4, and the signal of the line closest to HCCD 3 is accumulated in the buffer storage cell 5. Is done.

  Subsequently, in the period from t2 to t3 (= t1), the HCCD 3 receives the signal charges for one horizontal line transferred from the VCCD 2 by the two-phase driving pulses φH1 and φH2 applied to the transfer electrodes H1 and H2, respectively. The data is sequentially transferred to the output amplifier 4. The transferred signal charge is converted into a voltage by the output amplifier 4 and output as a CCD signal.

  By repeating the driving for one horizontal period as many times as the number of lines for transferring signals, an image of one screen can be acquired.

  Next, a second reading method (second reading mode) in the digital camera of the present embodiment will be described with reference to FIG. FIG. 4 is a timing chart showing a second reading method in which vertical transfer is performed within a horizontal transfer period of signal charges. The charge of PD1 is read to VCCD2 (not shown) in the column to which the charge read pulse is applied.

  In one horizontal period, the signal charges accumulated in the buffer storage cell 5 are transferred to the HCCD 3 through the transfer gate 6 in the period from t1 to t2.

  In the interval from t2 to t3 (= t1), the HCCD 3 sequentially outputs signal charges for one horizontal row transferred from the VCCD 2 by two-phase drive pulses φH1 and φH2 applied to the transfer electrodes H1 and H2, respectively. Forward to 4. The transferred signal charge is converted into a voltage by the output amplifier 4 and output as a CCD signal.

  Similarly, signal charges are sequentially transferred (vertical line shift) in the direction of HCCD 3 by the four-phase drive pulses φV 1 to φV 4 applied to the transfer electrodes V 1 to V 4 during the period t 2 to t 3 (= t 1), and are closest to the HCCD 3. The line signal is stored in the buffer storage cell 5. By repeating the driving for one horizontal period as many times as the number of lines for transferring signals, an image of one screen can be acquired.

  The second readout method is different from the first readout method in the timing of applying the four-phase vertical transfer pulse, and it is possible to significantly shorten the readout time by applying this within the horizontal transfer period. It is said. Therefore, the second reading method has an advantage of improving the continuous shooting speed by high-speed reading.

  On the other hand, disadvantages of the second reading method include an increase in crosstalk noise and peak current due to simultaneous superposition of horizontal transfer and vertical transfer. Further, there is a signal output fluctuation or the like due to the substrate voltage of the image sensor being swayed during the horizontal transfer period by the vertical transfer pulse.

  Among these adverse effects, noise and fluctuations in signal output are known to increase or decrease depending on the gain increase amount in the gain amplifier (amplifying means) of the preprocess circuit 15 because they are on the output of the CCD 12. Yes. It is also known that the fluctuation level and form of the signal output fluctuation due to the fluctuation of the substrate voltage varies depending on the temperature of the CCD 12.

  Next, a first reading method switching determination in the digital camera of the present embodiment will be described. FIG. 5 is a flowchart showing a first reading method switching determination processing procedure. First, the camera control unit 21 receives a signal from the operation unit 22 and determines whether or not the shooting mode is the single shooting mode (S101). When the shooting mode is the single shooting mode (YES in S101), the camera control unit 21 executes the first reading method (first reading mode) by the reading method switching function (S102). This is because there is no need for high-speed reading in the single-shot mode, and this is based on determinations to avoid various problems caused by the second reading method. Thereafter, the camera control unit 21 ends this process.

  On the other hand, when the shooting mode is the continuous shooting mode (NO in S101), the camera control unit 21 subsequently checks the set value of the gain increase amount in the gain amplifier of the preprocess circuit 15 and sets this value and the threshold value G1. Compare (S103). When the gain increase amount is larger than the threshold value G1 (YES in S103), the camera control unit 21 executes the first reading method by the reading method switching function (S104). This is based on a determination to avoid deterioration of image quality due to significant crosstalk noise and signal fluctuation, which are adverse effects of the second reading method, when the gain increase amount is large. Thereafter, the camera control unit 21 ends this process.

  On the other hand, when the gain increase amount is equal to or less than the threshold value G1 (less than the threshold value) (NO in S103), the camera control unit 21 executes the second reading method (second reading mode) by the reading method switching function ( S105). This is based on the determination for realizing the continuous shooting speed improvement by adopting the high-speed reading mode when the continuous shooting mode and the gain increase amount are small and the adverse effect of the second reading method is acceptable. Thereafter, the camera control unit 21 ends this process.

  According to the imaging apparatus of the first embodiment, it is possible to improve the continuous shooting speed by basically performing high-speed reading in the continuous shooting mode, and at the time of high gain or single shooting mode. By performing the reading method 1, it is possible to avoid degrading image quality.

[Second Embodiment]
Next, a second reading method switching determination in the digital camera of the second embodiment will be described. Since the configuration of the digital camera in the second embodiment is the same as that of the first embodiment, description thereof is omitted by using the same reference numerals.

  FIG. 6 is a flowchart showing a second reading method switching determination processing procedure in the second embodiment. First, the camera control unit 21 reads the remaining amount value measured by the battery remaining amount measuring unit 24 and compares it with a threshold value B1 (set value) (S201). When the remaining amount value is less than the threshold value B1 (YES in S201), the camera control unit 21 executes the first reading method by the reading method switching function (S202). This is because, when the remaining battery level is low, if the second reading method with high power consumption is executed, the number of storable images is reduced, and the determination for avoiding the possibility that the user may suffer disadvantages. by. Thereafter, the camera control unit 21 ends this process.

  On the other hand, when the remaining amount value is greater than or equal to the threshold value B1 (greater than or equal to the set value) (NO in S201), the camera control unit 21 reads the temperature of the temperature sensor unit 23, and this temperature, the threshold value T1, and the threshold value T1. The threshold value T2, which is a high temperature, is compared (S203). When the temperature is lower than the threshold value T1 or higher than the threshold value T2, that is, when the temperature is not within the predetermined range (YES in S203), the camera control unit 21 selects the first reading method by the reading method switching function. Execute (S204). This is based on a judgment for avoiding deterioration of the image quality because signal fluctuation, which is an adverse effect of the second reading method, is conspicuous when the temperature is extremely low or high. Thereafter, the camera control unit 21 ends this process.

  On the other hand, when the temperature is between the threshold value T1 and the threshold value T2, that is, when the temperature is within a predetermined range (NO in S203), the camera control unit 21 executes the second reading method by the reading method switching function. (S205). This is based on the determination for realizing the continuous shooting speed improvement by adopting the high-speed reading mode when the adverse effect of the second reading method is acceptable. Thereafter, the camera control unit 21 ends this process.

  According to the imaging apparatus of the second embodiment, when the remaining battery level is low, if the second reading method with high power consumption is executed, the number of images that can be shot decreases, and the user may suffer a disadvantage. You can avoid coming. In addition, when the temperature is extremely low or high, signal fluctuation, which is an adverse effect of the second reading method, is conspicuous, so that it is possible to avoid deterioration in image quality.

  Note that a processing procedure for making a determination similar to the above-described first reading method switching determination of FIG. 5 may be added to the processing of S205 of FIG. That is, the shooting mode is the continuous shooting mode, the gain increase amount of the gain amplifier of the preprocess circuit 15 is not more than the threshold value G1, the remaining battery level is not less than the threshold value B1, and the temperature is within a predetermined range (T1 ≦ temperature). In the case of ≦ T2), the second readout method may be switched. In other cases, the first readout method may be switched.

  As described above, in the imaging devices of the first and second embodiments, whether or not vertical / horizontal transfer overlap driving is performed according to parameters such as continuous shooting mode / single shooting mode, gain increase amount, temperature, and remaining battery level. It is possible to select. With this selection, it is possible to improve the continuous shooting speed under optimum conditions while minimizing the adverse effects such as crosstalk noise. Therefore, it is possible to provide an image pickup apparatus that is inexpensive, has a continuous shooting speed improvement, and is well-balanced in image quality without largely changing the structure of a commonly used solid-state image pickup element.

  The present invention is not limited to the configuration of the above-described embodiment, and any configuration can be used as long as the functions shown in the claims or the functions of the configuration of the present embodiment can be achieved. Is also applicable.

1 is a block diagram illustrating a schematic configuration of a digital camera according to a first embodiment. It is the figure which showed schematic structure of CCD12 as an interline type CCD. 10 is a timing chart showing a first reading method for performing vertical transfer outside a horizontal transfer period of signal charges. 10 is a timing chart showing a second reading method for performing vertical transfer within a horizontal transfer period of signal charges. It is a flowchart which shows the 1st reading method switching judgment processing procedure. It is a flowchart which shows the 2nd read-out method switching judgment processing procedure in 2nd Embodiment. It is a timing chart which shows the reading method of the signal charge in which the measure of the conventional reading time reduction is not performed. It is a timing chart which shows the reading method of the signal charge which implemented the measure of reading time reduction.

Explanation of symbols

1 PD (photodiode)
2 VCCD (vertical transfer path)
3 HCCD (horizontal transfer path)
4 Output amplifier 5 BS cell (buffer storage cell)
6 TG (Transfer Gate)
12 CCD
14 Image sensor driving device 15 Pre-process circuit 21 Camera control unit 23 Temperature sensor unit 24 Battery level measurement unit

Claims (2)

A plurality of photoelectric conversion elements arranged in a matrix, a vertical transfer path for vertical transfer of signal charges from the photoelectric conversion elements, and a horizontal transfer of the signal charges transferred by the vertical transfer path in the horizontal direction A solid-state imaging device having a horizontal transfer path to
Driving means for driving the solid-state imaging device by supplying a vertical transfer pulse for driving the vertical transfer path and a horizontal transfer pulse for driving the horizontal transfer path;
Amplifying means for amplifying an imaging signal output from the solid-state imaging device;
Setting means for setting the shooting mode;
When the single-shot mode is set by the setting means, the driving means is controlled so as to drive the solid-state imaging device by a first readout method for supplying the vertical transfer pulse outside the horizontal transfer pulse supply period. and, if the gain-up amount of the amplifying means together with the continuous shooting mode is set by said setting means is larger than a predetermined value, said drive means to drive the solid-state imaging device in the first read method And when the continuous shooting mode is set by the setting means and the gain increase amount of the amplifying means is equal to or less than the predetermined value, the second transfer pulse is supplied within the horizontal transfer pulse supply period. Control means for controlling the drive means so as to drive the solid-state imaging device by the readout method of:
An imaging apparatus comprising: A plurality of photoelectric conversion elements arranged in a matrix, a vertical transfer path for vertical transfer of signal charges from the photoelectric conversion elements, and a horizontal transfer of the signal charges transferred by the vertical transfer path in the horizontal direction A solid-state imaging device having a horizontal transfer path to
Driving means for driving the solid-state imaging device by supplying a vertical transfer pulse for driving the vertical transfer path and a horizontal transfer pulse for driving the horizontal transfer path;
Temperature measuring means for measuring the temperature of the solid-state imaging device;
A battery level measuring means for measuring the battery level;
When the remaining battery level measured by the remaining battery level measuring unit is less than a predetermined value, the solid-state imaging device is driven by the first readout method for supplying the vertical transfer pulse outside the horizontal transfer pulse supply period. when controlling the driving means so as to the remaining battery level measured by remaining battery level measuring means is measured by said temperature measuring means together with said at least a predetermined value the temperature is outside the predetermined range, the The driving unit is controlled to drive the solid-state imaging device by a first readout method, and the remaining battery level measured by the remaining battery level measuring unit is not less than the predetermined value and is measured by the temperature measuring unit. When the measured temperature is within the predetermined range, the solid-state imaging device is driven by a second readout method that supplies the vertical transfer pulse within the horizontal transfer pulse supply period. And control means for controlling the urchin said driving means,
An imaging apparatus comprising:

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