JP2005094469A - Image pickup apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To rapidly take still images consecutively without remarkably changing a basic structure thereof by employing a driving system for a rolling operation. <P>SOLUTION: This image pickup apparatus is provided with a focal plain shutter having a front curtain (21a) and a rear curtain (21b); an image pickup element (23) which has a light-receiving pixel region (23a) consisting of a plurality of pixels for accumulating optical charges and outputting signals, and performs start scanning of accumulated charges of optical charges of each pixel and signal output scanning of the accumulated optical charges in time series in the order same as the travelling directions of the front curtain and the rear curtain at the time of exposure; a first control means (30) for starting the travelling of the front curtain at an early timing by a time corresponding to the travelling time of the front curtain with respect to completion timing of the start of accumulating the optical charges in all the regions of the light-receiving region, and a second control means (30) for starting sequential output of the accumulated optical charge signals of the image pickup element synchronously with any later one of completion timing of start of accumulating the optical charges of the entire regions of the light-receiving pixel region and the timing of start of travelling of the rear curtain. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a technique for capturing a still image at high speed in an imaging apparatus using an XY address type image sensor.

  FIG. 5 is a diagram showing an overall circuit configuration of the XY address type image sensor.

  The MOS type image sensor includes a pixel unit 1, a vertical scanning circuit 2, a multiplexer 4, a noise suppression circuit 5, a horizontal scanning circuit 6, an output amplifier 7, a pixel cell power line 8, a pixel cell load 9, and a pixel cell load. It consists of a pulse line 10.

  In the pixel unit 1, pixel cells (PIX11, PIX12,...) That are photoelectric conversion cells are arranged in an array. The vertical scanning circuit 2 has signal lines (φV1, φV2,...) For selecting a row of pixel cells to be read. The multiplexer 4 receives external timing pulse signals from the reset pulse line 11 and the TR pulse line 12, and also sweeps out read pulse signal lines (φTR1, φTR2,...) For reading out accumulated charges of the pixel cells and unnecessary charges. It has reset pulse signal lines (φRST1, φRST2,...).

  The noise suppression circuit 5 receives the read pixel cell signal via the input lines (V1, V2,...), Corrects variations in the signal, and removes noise. The horizontal scanning circuit 6 has signal lines (φH1, φH2,...) For selecting a column of pixel cell signals, and controls horizontal selection switches (M101, M102,...) To output pixel cell signals. Sequentially sent to 7.

  The power line 8 of the pixel cell supplies a power voltage (VDDCEL) to the pixel cell. The pixel cell load 9 receives a signal from the load pulse line 10 of the pixel cell and controls the load of the pixel cell.

  Next, an outline of the rolling read operation will be described.

  FIG. 6 is a diagram showing a signal timing chart of the rolling read operation. FIG. 6 shows a power supply voltage (VDDCEL), a pixel cell load pulse line (LGCEL), a reset pulse line (RST), a readout pulse line (TR), a scanning circuit output capture pulse line (VDDRS), and a reset pulse signal line (φRST1). , ΦRST2,...) And readout pulse signal lines (φTR1, φTR2,...).

  After setting the power supply voltage (VDDCEL) to “high level”, a pulse signal is input to the reset pulse line (RST), and the reset pulse signal r11 is added to the reset pulse signal line φRST1 to sweep out unnecessary charges. Next, a pulse signal is input to the readout pulse line (TR), the readout pulse signal t1 is added to the readout pulse signal line (φTR1), and the charges accumulated in the pixel cells (PIX11, PIX21, PIX31) are read out, It sends out to the input lines (V1, V2, V3) of the noise suppression circuit 5.

  Next, after the power supply voltage (VDDCEL) is set to “low level”, a pulse signal is input to the reset pulse line (RST) and the reset pulse signal r12 is added to the reset pulse signal line φRST1, so that the pixel cells (PIX11, PIX21) are added. , PIX31) is prohibited until the next pulse signal (r21, t2, r22) is input.

  As a result, charges are accumulated in the pixel cells PIX11, PIX21, and PIX31 until the next pulse signal is input. That is, the interval between the read pulse signals t1 and t2 becomes the exposure time, and charges are accumulated.

  By sequentially executing the above operations for the reset pulse signal lines (φRST2, φRST3) and the read pulse signal lines (φTR2, φTR3), charge accumulation and reading can be performed for each row of pixel cells. By adopting a rolling readout operation that repeats charge accumulation and readout for each row of pixel cells, a through image can be captured at high speed.

  However, the technique described above is suitable for capturing a through image because it repeats charge accumulation and readout for each row of pixel cells, but for example, to capture a still image at high speed during continuous shooting in continuous shooting mode. Unsuitable. Therefore, there is a need for a technique that adopts a driving method related to a rolling operation and continuously captures still images at a high speed without greatly changing the basic structure.

  The present invention has been made in view of such circumstances, and an object of the present invention is to capture a continuous still image at high speed in an imaging apparatus employing a rolling readout method using an XY address type image sensor.

  An imaging apparatus according to a first aspect of the present invention has a focal plane shutter having a front curtain and a rear curtain that run independently, and a light-receiving pixel region that includes a plurality of pixels that accumulate photoelectric charges and output signals. In addition, a charge accumulation start scan and a signal output scan of the accumulated photocharges of each pixel are performed in time sequence in the same direction as the traveling direction of the front and rear curtains during exposure of the focal plane shutter. First control means for starting the front curtain at a timing earlier than the completion timing of the start of photoelectric charge accumulation in the entire area of the image sensor and the light receiving pixel area by a time corresponding to the travel time of the front curtain of the focal plane shutter And the accumulated photocharge signal stored in the image sensor in synchronization with the later timing of either the start timing of the start of photocharge accumulation in the entire light receiving pixel area or the start timing of the trailing curtain. ; And a second control means for starting the sequential output.

  According to a second aspect of the present invention, there is provided the imaging apparatus according to the second aspect, wherein in the imaging apparatus according to the above-described invention, the start scanning of the charge accumulation of the photoelectric charges of the pixels in the entire light receiving pixel region of the imaging element and the accumulated light The traveling time of the front and rear curtains of the focal plane shutter is shorter than the time required for the charge signal output scanning.

  According to a third aspect of the present invention, there is provided the imaging apparatus according to the third aspect, wherein the first control means opens the front curtain after the start of photoelectric charge accumulation scanning of the light receiving pixel region. Start it.

  According to a fourth aspect of the present invention, in the imaging device according to the above-described invention, each pixel of the imaging element resets the accumulated photocharge simultaneously with the signal output of the accumulated photocharge. Then, it is possible to start the next photocharge accumulation operation.

  According to a fifth aspect of the present invention, there is provided an imaging apparatus according to the fifth aspect, further comprising a mode selection unit that selects a continuous shooting mode in which continuous shooting is performed. The second control means performs the control when the continuous shooting mode is selected by the mode selection means.

  The imaging apparatus according to claim 6 of the present invention is the imaging apparatus according to the above-described invention, further comprising an exposure control means for starting the rear curtain after a predetermined time has elapsed from the start of the front curtain travel, Is determined based on the photometric value in the photometric means or the set input value of the shutter speed.

  According to the imaging apparatus of the present invention, continuous still images can be captured at high speed in an imaging apparatus that employs a rolling readout method using an XY address type image sensor.

  FIG. 1 is a block diagram showing a configuration of an imaging apparatus according to the present invention.

  The imaging apparatus includes a lens group 20 such as a zoom lens and a focus lens, a mechanical shutter 21, a drive circuit 22, an image sensor 23, a timing control unit 24, an image processing circuit 25, a display unit 26, and a media recording unit 27. .

  The mechanical shutter 21 is a focal plane shutter and includes a front curtain 21a and a rear curtain 21b, and a drive circuit 22 drives the front curtain 21a and the rear curtain 21b.

  The image sensor 23 is provided with a pixel portion 23a, a vertical scanning circuit 23b, and a horizontal scanning circuit 23c, and the timing control unit 24 supplies timing signals to the vertical scanning circuit 23b and the horizontal scanning circuit 23c.

  Further, the imaging apparatus includes a control unit 30, a photometry unit 31, a shutter speed setting unit 32, and an operation SW 33. The control unit 30 comprehensively controls each unit of the imaging apparatus, and automatically determines the shutter speed based on the photometric value in the photometric unit 31, or the set shutter set and input by the photographer from the shutter speed setting unit 32 The operation of the drive circuit 22 and the timing control means 24 is controlled according to the speed value. Further, the operation SW 33 is provided with a mode switch for setting a shooting mode for single shooting or continuous shooting.

  Next, the operation of the imaging apparatus when the photographer takes a picture in the continuous shooting mode will be described.

  FIG. 2 is a diagram for explaining the operation of the mechanical shutter 21 according to the embodiment of the present invention in correspondence with the rolling readout operation.

  An optical image of the subject is formed on the pixel unit 23 a by the lens group 20. The charges accumulated in the pixel cells by this optical image are read out row by row in the vertical scanning direction indicated by the arrow in FIG.

  On the other hand, the mechanical shutter 21 is a focal plane shutter. First, the front curtain 21a forms a light image on the pixel portion 23a while moving in the running direction indicated by the arrow in FIG. Subsequently, the rear curtain 21b operates in the traveling direction in FIG. 2 to close the shutter. Accordingly, the time difference between the front curtain 21a and the rear curtain 21b is the exposure time of each pixel cell.

  The present embodiment is characterized in that the traveling direction of the focal plane of the mechanical shutter 21 and the vertical scanning direction of the pixel portion 23a are arranged in the same direction.

  Next, a still image capturing operation by the imaging apparatus according to this configuration will be described.

  FIG. 3 is a time chart showing a still image capturing operation when the shutter speed is relatively slow.

  3 represents a state in which the control unit 30 controls the timing control means 24 to perform rolling reading. That is, by adding a readout pulse (TR1, TR2,..., TRn), an imaging signal is read out for each row of the pixel portion 23a.

  Therefore, when the mechanical shutter 21 is opened, the time interval at which the readout pulse is added becomes the exposure period. That is, in the pixel portion 23a, the accumulated photocharge is reset simultaneously with the signal output of the accumulated photocharge, and the next photocharge accumulation operation can be started. Part B of FIG. 3 is an image diagram of the exposure period represented by taking the row of the pixel part 23a on the vertical axis.

  3 represents a state in which the control unit 30 controls the drive circuit 22 to open and close the mechanical shutter. The control unit 30 predicts the operation timing of the read pulse TRn at the final stage, and controls the operation start of the front curtain 21a at a timing that is back by a predetermined time T2 from that timing. That is, the control unit 30 corresponds to the travel time T2 of the front curtain 21a of the focal plane shutter with respect to the operation timing of the read pulse TRn at the final stage, which is the completion timing of the start of photoelectric charge accumulation in the entire region of the pixel unit 23a. The drive circuit 22 is controlled so that the traveling of the front curtain 21a is started at a timing earlier by time.

  Next, the control unit 30 controls the drive circuit 22 so as to start the closing operation of the rear curtain 21b at the timing when the exposure time T1 has elapsed from the timing at which the front curtain 21a starts the opening operation. Here, the exposure time T1 may be calculated based on a photometric value in the photometric unit 32, or may be calculated based on a setting value set and input by the photographer from the shutter speed setting unit 32. Part D of FIG. 3 is an image diagram showing the exposure time by the mechanical shutter 21 by taking the row of the pixel part 23a on the vertical axis.

  Then, the control unit 30 controls the timing control means 24 in synchronization with the timing at which the trailing curtain 21b starts running, and adds the next read pulse (TR1, TR2,..., TRn). That is, sequential output of the photoelectric charge signal accumulated in the pixel portion 23a is started. Thereafter, the still image is captured by repeating the above-described operation.

  In order for the operation of the present embodiment to be established, the focal plane shutter has a longer time than the time required for the start scanning of the charge accumulation of the pixel of the pixel 23a and the signal output scan of the accumulated photocharge. It is a necessary condition that the traveling time of the front curtain 21a and the rear curtain 21b is short.

  FIG. 4 is a time chart showing a still image capturing operation when the shutter speed is relatively fast.

  4 shows a state in which the control unit 30 controls the timing control means 24 to perform rolling reading. That is, by adding a readout pulse (TR1, TR2,..., TRn), an imaging signal is read out for each row of the pixel portion 23a.

  Therefore, when the mechanical shutter 21 is opened, the time interval at which the readout pulse is added becomes the exposure period. That is, in the pixel portion 23a, the accumulated photocharge is reset simultaneously with the signal output of the accumulated photocharge, and the next photocharge accumulation operation can be started. Part B of FIG. 4 is an image diagram of the exposure period represented by taking the row of the pixel part 23a on the vertical axis.

  4 represents a state where the control unit 30 controls the drive circuit 22 to open and close the mechanical shutter. The control unit 30 predicts the operation timing of the read pulse TRn at the final stage, and controls the operation start of the front curtain 21a at a timing that is back by a predetermined time T2 from that timing. That is, the control unit 30 corresponds to the travel time T2 of the front curtain 21a of the focal plane shutter with respect to the operation timing of the read pulse TRn at the final stage, which is the completion timing of the start of photoelectric charge accumulation in the entire region of the pixel unit 23a. The drive circuit 22 is controlled so that the traveling of the front curtain 21a is started at a timing earlier by time.

  Next, the control unit 30 controls the drive circuit 22 so as to start the closing operation of the rear curtain 21b at the timing when the exposure time T1 has elapsed from the timing at which the front curtain 21a starts the opening operation. Here, the exposure time T1 may be calculated based on a photometric value in the photometric unit 32, or may be calculated based on a setting value set and input by the photographer from the shutter speed setting unit 32. 4 is an image diagram showing the exposure time by the mechanical shutter 21 by taking the row of the pixel portion 23a on the vertical axis.

  Then, the control unit 30 controls the timing control unit 24 in synchronization with the completion timing of the start of photoelectric charge accumulation in the entire region of the pixel unit 23a, and adds the next readout pulse (TR1, TR2,..., TRn). . That is, sequential output of the photoelectric charge signal accumulated in the pixel portion 23a is started. Thereafter, the still image is captured by repeating the above-described operation.

  In order for the operation of the present embodiment to be established, the focal plane shutter has a longer time than the time required for the start scanning of the charge accumulation of the pixel of the pixel 23a and the signal output scan of the accumulated photocharge. It is a necessary condition that the traveling time of the front curtain 21a and the rear curtain 21b is short.

  Note that the control unit 30 determines whether to capture a still image according to which time chart shown in FIG. 3 or FIG. 4 by comparing the exposure time T1 with a predetermined time T2 corresponding to the leading curtain travel time.

  That is, the control unit 30 determines the shutter speed based on the photometric value in the photometric unit 31 or the set input value from the shutter speed setting unit 32 to obtain the exposure time T1, and further determines in advance from the operating time of the front curtain 21a. Time T2 is obtained.

  When T1> T2, the control unit 30 captures a still image according to the time chart shown in FIG. 3, and when T1 ≦ T2, the control unit 30 captures a still image according to the time chart shown in FIG.

  According to each embodiment described above, the driving sequence is configured with the traveling direction of the focal plane shutter and the vertical scanning direction of the image sensor as the same direction, and the operation of the focal plane shutter and the signal reading operation are overlapped. This makes it possible to shorten the time for capturing still images.

  Furthermore, in each embodiment, since the driving method related to the conventional rolling readout operation is adopted without changing, still images can be captured continuously at high speed without greatly changing the conventional basic driving method. it can.

  Further, the present embodiment can be configured to operate when the continuous shooting mode is selected from the operation SW 33, but it goes without saying that the present embodiment can also be applied to shooting modes other than the continuous shooting mode.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Further, various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, you may combine suitably the component covering different embodiment.

1 is a block diagram illustrating a configuration of an imaging apparatus according to the present invention. The figure explaining operation | movement of a mechanical shutter corresponding to rolling reading operation | movement. 6 is a time chart showing a still image capturing operation when the shutter speed is relatively slow. Time chart showing still image capture operation when shutter speed is relatively fast The figure which shows the whole circuit structure of an XY address type image sensor. The figure which shows the drive timing chart of rolling reading.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 21 ... Mechanical shutter, 21a ... First curtain, 21b ... Rear curtain, 22 ... Drive circuit, 23 ... Image sensor, 23a ... Pixel part, 23b ... Vertical scanning circuit, 23c ... Horizontal scanning circuit, 24 ... Timing control means, 30 ... Control unit.

Claims (6)

A focal plane shutter having a front curtain and a rear curtain that run independently;
It has a light-receiving pixel area consisting of a plurality of pixels for accumulating photoelectric charges and outputting signals, and the light of each pixel is time-sequentially in the same direction as the traveling direction of the front and rear curtains during exposure of the focal plane shutter. An image sensor that performs a charge accumulation start scan of charges and a signal output scan of accumulated photocharges;
First control means for starting traveling of the front curtain at a timing earlier by a time corresponding to the traveling time of the front curtain of the focal plane shutter than the completion timing of the start of photoelectric charge accumulation in the entire light receiving pixel region;
Second control for starting the sequential output of the photoelectric charge signals accumulated in the image sensor in synchronization with the later timing of either the completion timing of the start of photoelectric charge accumulation in the entire area of the light-receiving pixel area or the start timing of the trailing curtain. And an imaging device.   The traveling time of the front and rear curtains of the focal plane shutter is shorter than the time required for the charge accumulation start scanning of the pixels in the entire light receiving pixel region of the image sensor and the signal output scanning of the accumulated photoelectric charges. The imaging apparatus according to claim 1.   The imaging apparatus according to claim 2, wherein the first control unit starts a front curtain after the start of photoelectric charge accumulation scanning of the light receiving pixel region.   2. Each pixel of the image pickup device is capable of resetting the accumulated photocharge simultaneously with the signal output of the accumulated photocharge and entering the next photocharge accumulation operation. The imaging device described. Comprising mode selection means for selecting a continuous shooting mode for continuous shooting;
The imaging apparatus according to claim 1, wherein the first control unit and the second control unit perform the control when a continuous shooting mode is selected by the mode selection unit. Exposure control means for starting the trailing curtain after a predetermined time has elapsed from the start of the leading curtain running,
2. The imaging apparatus according to claim 1, wherein the predetermined time is determined based on a photometric value in a photometric unit or a set input value of a shutter speed.

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