JP2008028757A - Solid-state image pickup device and camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To actualize a sold-state image pickup device which is suitable for real-time live view display for a camera and can quickly read image signals, and the camera. <P>SOLUTION: The solid-state image pickup device acquires image signal components and dark signal components from a plurality of pixels that are two-dimensionally arranged in horizontal and vertical directions, and outputs differential signals between the image signals and dark signals. The solid-state image pickup device acquires only the image signal components for a period of one-line reading when reading real-time live view, and then outputs them. The camera is provided with the solid-state image pickup device. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a solid-state imaging device and a camera used for a digital camera or the like.

  In recent years, in a digital camera using a solid-state imaging device, a liquid crystal screen that displays a subject image in real-time live view is often used instead of an optical viewfinder in order to determine the composition of the subject. This is already common especially in a compact type digital camera, but recently, it is also demanded for an expensive and high-quality single-lens reflex digital camera.

  In addition, solid-state imaging devices used for single-lens reflex digital cameras have become mainstream in which the number of pixels is 6 million pixels to 10 million pixels or more in order to satisfy the demand for high image quality. Although a high-resolution solid-state imaging device can achieve high-resolution image output in this way, on the other hand, the number of pixels that can be output per second on average is about 3 to 5 frames / second because of the large number of pixels. . Also, in a high-speed single-lens reflex digital camera, the maximum number of frames that can be output per second is about 8 frames / second.

  On the other hand, in order to realize real-time live view display of the subject on the camera's LCD screen, if the speed of 30 to 60 frames / second, which is at least equivalent to the moving image speed, cannot be realized, the operation of determining the composition of the photographer is performed. Image output cannot follow, and real-time live view display of the subject image cannot be realized. Therefore, in general, not all signals obtained at each pixel, that is, all pixel signals are used for image output, but the number of frames that can be output per second is reduced by reducing the number of pixels by using pixel signals. Real-time live view display is performed by increasing.

In general, in a solid-state imaging device used in a single-lens reflex digital camera, a pixel signal obtained by receiving subject light and a dark signal obtained immediately after resetting the pixel are output for each pixel, and a difference between these is output. By using this to generate an image, noise can be removed and image quality can be improved (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 1-154678

  However, in the conventional solid-state imaging device as disclosed in Patent Document 1, it is necessary to provide a period for reading the above-described pixel signal and dark signal in one horizontal period. For this reason, there is a limit to shortening one horizontal period, and there is a problem that it is difficult to increase the number of frames that can be output per second in order to realize real-time live view display.

  Accordingly, the present invention has been made in view of the above problems, and provides a solid-state imaging device and a camera that are suitable for real-time live view display of a camera and capable of reading an image signal at high speed. .

  In order to solve the above problems, the present invention acquires an image signal component and a dark signal component from a plurality of pixels arranged two-dimensionally in a horizontal direction and a vertical direction, and obtains a difference signal between the image signal and the dark signal. A solid-state imaging device that outputs and outputs only the image signal component during one horizontal readout period at the time of real-time live view readout.

  The present invention also provides a camera having the solid-state imaging device.

  ADVANTAGE OF THE INVENTION According to this invention, the solid-state imaging device and camera which can read the image signal suitable for the real-time live view display of a camera at high speed are realizable.

  Hereinafter, a solid-state imaging device and a camera according to embodiments of the present invention will be described in detail with reference to the accompanying drawings.

(First embodiment)
FIG. 1 is a block diagram illustrating a configuration of a single-lens reflex digital camera including a solid-state imaging device according to the first embodiment of the present invention.

  As shown in FIG. 1, the single-lens reflex digital camera 1 includes a camera lens 2 and a half mirror 3 in order from a subject side (not shown), and a finder prism 4 and a finder 5 on a reflected light path of the half mirror 3. Is provided. In addition, a solid-state imaging device 6 that will be described in detail later and a camera system control unit 7 that controls the operation of the entire camera are provided on the transmission optical path of the half mirror 3.

  Further, in the single-lens reflex digital camera 1, a focus detection unit 8, an image processing unit 9 that reads an image signal from the solid-state imaging device 6 and performs image processing such as color correction, a storage unit 10, and a lens that drives a camera lens. A control unit 11 is provided. On the back of the single-lens reflex digital camera 1 main body, an operation panel 12 for performing shutter operation and flash setting, a photographed image, and a subject image in real-time live view are displayed for determining a composition during photographing. A liquid crystal display unit 13 and a memory card 14 are provided.

  The single-lens reflex digital camera 1 is equipped with a dedicated module for AF (not shown). The solid-state image pickup device 6 is a CMOS solid-state image pickup device that is one of the amplification type solid-state image pickup devices. The solid-state image pickup device 6 can read a signal of an arbitrary selected unit pixel and can be speeded up. Have.

  Under the above configuration, light from a subject (not shown) enters the half mirror 3 via the camera lens 2, a part of the light is reflected to the finder prism 4, and the light transmitted through the half mirror 3 is solid. An image is formed on the imaging device 6. The light imaged on the solid-state imaging device 6 is converted into an electrical signal and output to the image processing unit 9 as an image signal. The image processing unit 9 performs appropriate image processing such as color correction and image compression, and outputs an image signal to the camera system control unit 7.

  Then, the camera system control unit 7 outputs the received image signal to the storage unit 10, temporarily stores the image signal, and stores the image signal in the memory card 14 as necessary. The camera system control unit 7 reads the image signal temporarily stored in the storage unit 10 and displays the image on the liquid crystal display unit 13 in accordance with the operation of the operation panel 12.

  Next, a driving method of the solid-state imaging device 6 that is the most characteristic in the present embodiment will be described in detail.

  FIG. 2 is a diagram illustrating a configuration of the solid-state imaging device according to the first embodiment of the present invention.

  As shown in FIG. 2, the solid-state imaging device according to this embodiment includes a pixel unit 20 composed of pixels of n rows and m columns, and vertical scanning that outputs a drive signal to each pixel of the pixel unit 20 for each row. The circuit 22 includes a horizontal scanning circuit 21 that outputs a drive signal for each column, and a signal processing circuit 23 that reads an output signal from each pixel through a vertical signal line.

  First, in the single-lens reflex digital camera 1 including the solid-state imaging device 6 having such a configuration, the device 6 when reading out an image signal from the solid-state imaging device 6 in order to display the photographed subject image on the liquid crystal display unit 13. The driving procedure will be described.

  FIG. 3 is a diagram showing drive timings when reading out an image signal for displaying a photographed subject image on the liquid crystal display unit 13 in the solid-state imaging device 6 according to the first embodiment of the present invention.

  As shown in FIG. 3, in the solid-state imaging device 6, the camera system control unit 7 inputs a control signal φVn to the vertical scanning circuit 22. Thereby, the pixel unit 20 selects which row of the pixel group output signals are read out.

  Next, the camera system control unit 7 inputs a control signal φDark to the signal processing circuit 23. As a result, a dark signal is read from each pixel in the previously selected row, and is temporarily stored in a dark signal hold circuit (not shown) in the signal processing circuit 23 (for example, a capacitor). Note that the dark signal is a signal including fixed pattern noise obtained in each pixel when the pixel unit 20 is reset.

  Further, the camera system control unit 7 inputs a control signal φSig to the signal processing circuit 23. As a result, like the dark signal, the pixel signal is read from each pixel in the previously selected row, and is temporarily stored in a pixel signal hold circuit (for example, a capacitor) (not shown) in the signal processing circuit 23.

  Then, the camera system control unit 7 inputs a start signal φSTH for driving the horizontal scanning circuit 21 to the horizontal scanning circuit 21. Based on this, the horizontal scanning circuit 21 inputs the control signal φHn to the signal processing circuit 23 in order from H1 to Hn. As a result, the signal processing circuit 23 sequentially reads out the pixel signal and the dark signal accumulated in the pixel signal hold circuit and the dark signal hold circuit, takes the difference between them, and outputs it as an image signal Vout. That is, the image signal Vout is a high-quality image signal from which fixed pattern noise and the like are removed.

  By repeatedly reading the image signal Vout as described above while being shifted in the vertical direction by the vertical scanning circuit 22, the image signal for one frame can be read. The image signal for one frame is input to the liquid crystal display unit 13 via the image processing unit 9 and the camera system control unit 7 as described above, so that the photographed subject image is displayed on the liquid crystal display unit 13. It will be. This signal is stored in the memory card 14 via the storage unit 10 as a still image. The display of the captured subject image on the liquid crystal display unit 13 is hereinafter referred to as normal display of the subject image.

  Next, in order to display a subject image on the liquid crystal display unit 13 in the real-time live view display in the single-lens reflex digital camera 1, a driving procedure of the device 6 when reading out an image signal from the solid-state imaging device 6 at high speed will be described.

  FIG. 4 is a diagram illustrating drive timings when the image signal for performing the real-time live view display of the subject image is read at high speed in the solid-state imaging device according to the first embodiment of the present invention.

  In the solid-state imaging device 6, the camera system control unit 7 inputs a control signal φVn to the vertical scanning circuit 22. Thereby, the pixel unit 20 selects which row of the pixel group output signals are read out.

  Then, the camera system control unit 7 inputs a control signal φSig to the signal processing circuit 23. As a result, the pixel signal is read from each pixel in the previously selected row and temporarily stored in a pixel signal hold circuit (not shown) in the signal processing circuit 23.

  Further, the camera system control unit 7 inputs a start signal φSTH for driving the horizontal scanning circuit 21 to the horizontal scanning circuit 21. Based on this, the horizontal scanning circuit 21 inputs the control signal φHn to the signal processing circuit 23 in order from H1 to Hn. As a result, the signal processing circuit 23 sequentially reads out the pixel signals accumulated in the pixel signal hold circuit and outputs them as an image signal Vout.

  By repeatedly reading the image signal Vout as described above while being shifted in the vertical direction by the vertical scanning circuit 22, the image signal for one frame can be read. As described above, by reading out only the pixel signal without reading out the dark signal in the period of reading out the image signal of the pixel group in an arbitrary row in the pixel unit 20, that is, in one horizontal period, compared to the case of normal display of the subject image. 1 horizontal period can be greatly shortened. For this reason, it is possible to read out pixel signals at high speed, and it is possible to improve the number of frames that can be output per second. Therefore, it is possible to realize smoother real-time live view display of a subject image by repeatedly reading out the image signal for one frame described above and inputting it to the liquid crystal display unit 13 at high speed.

(Second Embodiment)
Next, a single-lens reflex digital camera including a solid-state imaging device according to a second embodiment of the present invention will be described.

  Since the basic configuration of the single-lens reflex digital camera provided with the solid-state imaging device according to the present embodiment is the same as that of the first embodiment, the description of the same parts and the drawings are omitted, and the most characteristic solid-state imaging device The configuration and driving method will be described in detail. In the solid-state imaging device, the same parts as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted.

  FIG. 5 is a diagram illustrating a configuration of a solid-state imaging apparatus according to the second embodiment of the present invention.

  As shown in FIG. 5, the solid-state imaging device 106 acquires the pixel signal Vsig and the dark signal VDark from the pixel unit 20, and a storage unit 24 for storing the dark signal VDark is provided on the output side of the dark signal VDark. Is provided. A subtraction circuit 25 is provided on the output side of the pixel signal Vsig so that the dark signal VDark from the storage unit 24 is input and a difference signal (Vout) between the pixel signal Vsig and the dark signal VDark is output. Has been.

  When performing normal display of the subject image in the solid-state imaging device 106 having such a configuration, the driving procedure of the device 106 for reading out the image signal is the same as that in the first embodiment, and thus the real-time live view of the subject image is displayed. A driving procedure of the device 106 for reading out an image signal at high speed when performing display will be described below.

  FIG. 6 is a diagram showing drive timings when reading out an image signal for performing real-time live view display of a subject image at high speed in the solid-state imaging device according to the second embodiment of the present invention.

  While the first embodiment is configured to read out only pixel signals in one horizontal period, the solid-state imaging device 106 has only one horizontal period A in which only pixel signals are read and only dark signals as shown in FIG. 1 horizontal period B is read out, and dark signal readout (1 horizontal period B) is periodically performed in the process of repeating readout of only pixel signals (1 horizontal period A).

  Here, a driving procedure of the solid-state imaging device 106 when only the pixel signal is read in one horizontal period A will be described below.

  As shown in FIG. 6, the camera system control unit 7 inputs a control signal φVn to the vertical scanning circuit 22. Thereby, the pixel unit 20 selects which row of the pixel group output signals are read out.

  Then, the camera system control unit 7 inputs a control signal φSig to the signal processing circuit 21. As a result, the pixel signal is read from each pixel in the previously selected row and temporarily stored in a pixel signal hold circuit (not shown) in the signal processing circuit 23.

  Further, the camera system control unit 7 inputs a start signal φSTH for driving the horizontal scanning circuit 21 to the horizontal scanning circuit 21. Based on this, the horizontal scanning circuit 21 inputs the control signal φHn to the signal processing circuit 23 in order from H1 to Hn. As a result, the signal processing circuit 23 sequentially reads out the pixel signals accumulated in the pixel signal hold circuit and outputs them as the pixel signal VSig.

  A driving procedure of the solid-state imaging device 106 when only a dark signal is read in one horizontal period B will be described below.

  As shown in FIG. 6, the camera system control unit 7 inputs a control signal φVn to the vertical scanning circuit 106. Thereby, the pixel unit 20 selects which row of the pixel group output signals are read out.

  Then, the camera system control unit 7 inputs a control signal φDark to the signal processing circuit 23. As a result, a dark signal is read from each pixel in the previously selected row and is temporarily stored in a dark signal hold circuit (not shown) in the signal processing circuit 23.

  Further, the camera system control unit 7 inputs a start signal φSTH for driving the horizontal scanning circuit 21 to the horizontal scanning circuit 21. Based on this, the horizontal scanning circuit 21 inputs the control signal φHn to the signal processing circuit 23 in order from H1 to Hn. As a result, the signal processing circuit 23 sequentially reads out the dark signals accumulated in the dark signal hold circuit and outputs them as the dark signal VDark.

  Based on the above driving procedure, the readout of the pixel signal VSig is repeatedly performed while being shifted in the vertical direction by the vertical scanning circuit 22, and during the readout of the pixel signal VSig, the dark signal VDark is read out at a predetermined cycle. The read dark signal VDark is temporarily stored in the storage unit 24 and is output to the subtraction circuit 25 every time the pixel signal VSig is read. As a result, the subtraction circuit 25 obtains the difference between the pixel signal VSig and the dark signal VDark and outputs the image signal VSig−VDark. By repeatedly reading out the image signal VSig-VDark in this way, an image signal for one frame can be obtained. The image signal VSig-VDark becomes a high-quality image signal from which fixed pattern noise and the like are removed. The dark signal VDark stored in the storage unit 24 is updated every time the dark signal VDark is read.

  As described above, in the solid-state imaging device 106 according to the present embodiment, by reading out only the pixel signal without reading out the dark signal in one horizontal period A, the one horizontal period A is significantly shortened as in the first embodiment. be able to. Then, the quality of the image signal can be improved by periodically reading out the dark signal in one horizontal period B and taking the difference for each pixel signal. Thus, according to the solid-state imaging device 106, real-time live view display of a subject image can be realized with good image quality. In the above description, the case of acquiring a dark signal for one row has been described. However, the dark signal for one pixel can be stored and used as a representative, or the dark signal for all pixels can be used. Can be stored in the storage unit 24, and a difference from the corresponding pixel signal can be obtained and output.

  As described above, according to each embodiment, a solid-state imaging device capable of reading an image signal at high speed can be realized. In addition, a digital camera capable of real-time live view display can be realized by using high-speed reading of the image signal. This real-time live view display is particularly useful when determining a composition before taking a picture.

1 is a block diagram illustrating a configuration of a single-lens reflex digital camera including a solid-state imaging device according to a first embodiment of the present invention. It is a figure which shows the structure of the solid-state imaging device which concerns on 1st Embodiment of this invention. In the solid-state imaging device which concerns on 1st Embodiment of this invention, it is a figure which shows the drive timing at the time of reading the image signal for displaying the image | photographed subject image on a liquid crystal display part. FIG. 6 is a diagram illustrating drive timings when an image signal for performing real-time live view display of a subject image is read at high speed in the solid-state imaging device according to the first embodiment of the present invention. It is a figure which shows the structure of the solid-state imaging device which concerns on 2nd Embodiment of this invention. It is a figure which shows the drive timing in the case of reading the image signal for performing the real-time live view display of a to-be-photographed image at high speed in the solid-state imaging device which concerns on 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Single lens reflex digital camera 2 Camera lens 3 Half mirror 4 Finder prism 5 Finder 6, 106 Solid-state imaging device 7 Camera system control part 8 Focus detection part 9 Image processing part 10 Memory | storage part 11 Lens control part 12 Operation panel 13 Liquid crystal display part DESCRIPTION OF SYMBOLS 14 Memory card 20 Pixel part 21 Horizontal scanning circuit 22 Vertical scanning circuit 23 Signal processing circuit 24 Memory | storage part 25 Subtraction circuit

Claims (4)

In a solid-state imaging device that obtains an image signal component and a dark signal component from a plurality of pixels arranged two-dimensionally in a horizontal direction and a vertical direction, and outputs a difference signal between the image signal and the dark signal.
A solid-state imaging device, wherein only the image signal component is acquired and output during one horizontal readout period at the time of real-time live view readout.   While only acquiring the image signal component during one horizontal readout period during the real-time live view readout, further acquiring only the dark signal component during the one horizontal readout period at a predetermined interval, The solid-state imaging device according to claim 1, wherein a difference signal of the dark signal component is output.   The solid-state imaging device according to claim 2, further comprising a storage unit that stores the dark signal component acquired at a predetermined interval.   A camera comprising the solid-state imaging device according to claim 1.

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