JP2009124260A - Imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging apparatus which allows flash photographing in a rolling shutter system without degrading the image quality. <P>SOLUTION: The imaging apparatus includes: an illumination part 127 for illuminating light; a photographic optical system 106 for imaging a subject image; an image sensor 104 which converts the subject image imaged by the photographic optical system to an electric signal by pixel signals of pixels two-dimensionally arranged and outputs the electric signal in an XY address system; an image processing part 110 which converts the output of the image sensor to a prescribed form: storage parts 126 and 128 wherein signals processed by the image processing part are stored; and an exposure means which starts exposure in response to resets per row of the image sensor and terminates exposure in response to reading-out of pixel signals. When partial optical elements of the photographic optical system are intermittently moved and illuminating light is continuously radiated from the illuminating part to consecutively take a plurality of images, a read frame period of the image sensor is varied in accordance with positions of the optical elements. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an imaging apparatus using a CMOS image sensor as an imaging element.

2. Description of the Related Art In recent years, an image pickup apparatus such as a digital camera has fixed a CMOS image sensor that converts a subject image formed by a photographing optical system into electrical signals by using two-dimensionally arranged pixel signals and outputs the electrical signals using an XY address method. It is used as an image sensor. CMOS image sensors have an exposure method called a rolling shutter. This exposure method is a method in which the exposure is started by stopping the output of the electronic shutter, that is, stopping the discharge of the electric charge, and the exposure is ended by reading out the pixel data, but the exposure start timing and the exposure end timing are sequentially set for each pixel row of the solid-state imaging device. It differs from a CCD, which is another form of solid-state imaging device that performs simultaneous accumulation exposure, in terms of deviation.
For this reason, when the exposure time is short, the exposure common time zone in which all the lines of the image sensor accumulate simultaneously may be short or may not exist. Shooting with the flash of the strobe, which is the illumination unit, requires light emission control during this common exposure time zone, and if light is emitted at a timing outside the common exposure time zone, there are lines that can accumulate charges due to the strobe light component and lines that cannot be accumulated. And an abnormal image with different exposure on the top and bottom in one screen.
Therefore, in Patent Document 1, when simultaneous exposure is required as in flash photography, a common time zone for exposure is secured by thinning out pixel rows of a CMOS image sensor.

JP 2004-147278 A

Although the common exposure time zone can be secured in the contents described in Patent Document 1, the number of recorded pixels is reduced when a still image is taken to reduce the pixel row of a CMOS image sensor used for imaging, and the image quality is sensed. You won't get.
In the rolling shutter system, since exposure and readout are not separated on the time axis, immediately after switching the readout drive system, the accumulated charge remains only in the light receiving element on the upper side of the screen until just before the switching. For this reason, an invalid frame that cannot be used for display or information acquisition occurs immediately after the drive is switched, and some of the optical elements of the photographing optical system are moved, and illumination light is continuously emitted from the illumination unit. However, when focus bracket shooting is performed in which a plurality of images are continuously captured, a reduction in shooting interval becomes a new problem.

An object of the present invention is to provide an imaging apparatus that can perform strobe shooting using a rolling shutter system without reducing image quality.
It is an object of the present invention to provide an imaging apparatus capable of performing flash photography with an optimal exposure state corresponding to each focal length of focus bracket photography in which a plurality of images are continuously taken with a rolling shutter system. To do.

  In order to achieve the above object, a first imaging apparatus according to the present invention includes an illumination unit that emits light, a photographing optical system that forms a subject image, and a two-dimensionally arranged pixel signal in the photographing optical system. An image sensor that converts an image of a subject image into an electrical signal and outputs the electrical signal using an XY address method, an image processing unit that converts an output of the image sensor into a predetermined format, and a signal processed by the image processing unit In an imaging apparatus having a storage unit for storing image data, an exposure unit that starts exposure by resetting the image sensor in units of rows and ends exposure by reading pixel signals is used. When a plurality of images are continuously captured while moving intermittently and continuously illuminating illumination light from the illumination unit, the readout frame period of the imaging element is changed according to the position of the optical element. To let It is a symptom.

  In the first imaging device, changing the readout frame period of the imaging element is to make the exposure frame period longer than the readout frame period in order to change the exposure common time of all the rows of the imaging element. Yes.

  In the first imaging device, when a plurality of images are continuously captured while intermittently moving some of the optical elements of the photographing optical system and continuously illuminating the illumination light from the illumination unit The longer the exposure frame period, the higher the amount of illumination light emitted from the illuminating unit.

  In the first imaging apparatus, when shooting with illumination light from the illumination unit, the exposure frame period is adjusted to match the emission time of the illumination light in order to match the exposure common time of all rows of the image sensor. It is a feature.

  A second imaging device according to the present invention electrically illuminates a subject image formed by a photographing optical system with each of two-dimensionally arranged pixel signals, an illumination unit that emits light, a photographing optical system that forms a subject image. An image sensor that converts the signal into an XY address method, an image processor that converts the output of the image sensor into a predetermined format, and a storage that stores the signal processed by the image processor The imaging apparatus has an exposure unit that starts exposure by resetting the image sensor in units of rows and ends exposure by reading out pixel signals. When shooting with illumination light from the illumination unit, The exposure frame period is longer than the readout frame period in order to lengthen the exposure common time of all rows.

  In the second imaging apparatus, when the illumination light is pre-illuminated from the illumination unit for dimming before still image shooting, the dimming frame period is set to be the same as the normal shooting frame period and is centered on the recording image coordinates of the image sensor. The irradiation is performed during the exposure period of the corresponding line.

  According to the present invention, when capturing a plurality of images continuously while intermittently moving some optical elements of the photographing optical system and continuously irradiating illumination light from the illumination unit, Since the readout frame period of the image sensor is changed in accordance with the position of the element, it is possible to realize strobe photography with an optimal exposure state corresponding to each focal length of photography in which a plurality of images are taken continuously.

  According to the present invention, when photographing with illumination light from the illumination unit, the exposure frame period is made longer than the readout frame period in order to lengthen the exposure common time of all rows of the image sensor. Rolling is a method that does not require thinning out the pixel rows of the image sensor, and is an exposure means that starts exposure by resetting the image sensor in units of rows and ends exposure by reading out pixel signals without reducing image quality. Flash photography can be realized with the shutter method.

  Embodiments according to the present invention will be described below with reference to the drawings. FIG. 1 shows a configuration of an image pickup apparatus according to the present invention, which is formed by a strobe unit 127 serving as an illumination unit that emits light, a photographing optical system 107 that forms a subject image, and a photographing optical system 107. A CMOS image sensor 104 serving as an image pickup device that converts the subject image into an electrical signal and outputs it, an image processing unit 110 that converts the output of the CMOS image sensor 104 into a predetermined format, and a signal processed by the image processing unit 110 Are provided with a recording medium 128 and an image buffer memory 126 as storage units, and a control calculation unit 120 as control means.

  The optical unit 100 includes a lens 101 serving as an optical element of the photographing optical system 107, an aperture / shutter 102, an optical low-pass filter 103, a CMOS image sensor 104, and a focus mechanism 105 for the lens 101. The focal length of the lens 101 is arbitrarily changed mechanically by changing the position of the lens 101 by the focus mechanism 105 at the time of focusing and at the time of starting and stopping the imaging apparatus. The aperture / shutter 102 is switched to an appropriate aperture diameter at the time of shooting, and performs a closing operation and an opening operation as a shutter at the time of still image shooting. The aperture / shutter 102 and the focus mechanism 105 are driven by an optical system driving unit 106.

  The CMOS image sensor 104 converts an object image formed on the lens 101 by each pixel signal arranged two-dimensionally into an electric signal, and outputs the electric signal by an XY address method. In other words, the CMOS image sensor 104 converts an optical image formed by the light receiving element units arranged in two dimensions into a charge atom, and outputs it as an electric signal to the outside at the read timing transmitted from the drive unit 104A.

  The control calculation unit 120 includes a known computer, and includes an optical unit 100, an image processing unit 110 including an input processing block 111 and an image processing block 112, an optical system driving unit 106, a program memory 121, an operation unit 122, An LCD panel 123 serving as a display unit and a strobe unit 127 are connected via a signal line. A compression / decompression processing unit 124, an image recording I / F unit 125, and an image buffer memory 126 are connected to the control arithmetic unit 120 via a bus.

  The control calculation unit 120 gives a driving instruction to the optical system driving unit 106 according to the photographing mode stored in the program memory 121 in advance, and adjusts the focal length of the lens and the light amount by the aperture / shutter 102. From the control operation unit 120, an imaging clock signal, a vertical synchronization signal, and a horizontal synchronization signal are input to the drive unit 104A of the CMOS image sensor 104. Further, the control calculation unit 120 has a function of changing the cycle of the vertical synchronization signal and a function of controlling the light emission of the strobe unit 127 in response to the change of the cycle. In this embodiment, the CMOS image sensor 104 is controlled by the control arithmetic unit 120 so as to constitute a rolling shutter that is a well-known exposure unit that starts exposure by resetting in units of rows and ends exposure by reading pixel signals. Is done.

  In the imaging apparatus, the signal output from the CMOS image sensor 104 is subjected to image processing in a predetermined format by the image processing unit 110, and the recorded image is finally passed through the compression / expansion processing unit 124 and the image recording I / F unit 125. Is stored in the recording medium 128 in a predetermined file format. In this embodiment, examples of the recording medium 128 include media such as an SD card, a compact flash (registered trademark) card, and an XD picture card. Examples of the file format include well-known JPEG images. However, the recording medium 128 is limited to these media and file formats. Not what you want.

  When the imaging device is used in a monitor state before recording on the recording medium 128, the imaging device is processed as a display image by the image processing unit 110, displays an image on the LCD panel 123, and displays the displayed image. Display updated as needed. The strobe unit 127 controls the charge of the strobe charge, the light emission timing, and the light emission time in accordance with instructions from the control calculation unit 120.

Next, the operation of the imaging apparatus by the control calculation unit 120 of the present invention will be described using the timing charts shown in FIGS.
In the timing charts shown in the drawings, the top shows the timing of the vertical synchronization signal, and the bottom shows the timing of each line in the recording area (or effective pixel area) of the CMOS image sensor 104. In each timing chart, the blacked area is a period during which the charge in the light receiving element is discharged to the substrate because the electronic shutter (rolling shutter) of the CMOS image sensor 104 is output, and the whitened area is the same electronic shutter. Corresponds to an exposure period in which charges are accumulated in the light receiving element. The accumulated charge is read out immediately before the start of the black electronic shutter output period. The dotted line during the still image exposure frame period indicates the exposure common time tn.

  The control calculation unit 120 performs control so as to change the period of the vertical synchronization signal indicated by the symbol Vn in order to make the exposure frame period longer than other frames and to increase the exposure common time tn.

  FIG. 2 shows a timing chart before changing the period of the vertical synchronizing signal. Since the vertical synchronization signal V0 in FIG. 2 is the same, when the exposure time is short, the exposure common time period t0 in which all the lines of the image sensor accumulate simultaneously is short. With such a period, the strobe unit 127 emits light. Opportunities for shooting are limited.

  FIG. 3 shows a timing chart of the control according to claim 5 of the present invention. In the prior art, strobe photography was difficult because the time difference between the start of exposure of the last line and the reading of the first line was short, but here, the period of the vertical synchronization signal (exposure frame period) is set to V0 <V1, so that exposure is common. The time zone can be expanded to t0 <t1. For this reason, a margin can be provided in the light emission time by the strobe unit 127 indicated by the reference symbol X1, and strobe photography using the rolling shutter system can be performed without reducing the image quality as in the prior art.

  FIG. 4 shows a timing chart of the control according to claim 4 of the present invention. When shooting with illumination light from the strobe unit 127, in order to match the exposure common time t2 of all the rows of the CMOS image sensor 104, the period of the vertical synchronization signal (period of the exposure frame period) is set to the emission time of the illumination light. It is adjusted together.

  The amount of light emitted by the strobe unit 127 depends on the light emission time (X1, X2), and a vertical synchronization signal is provided so that an exposure common time (t1, t2) slightly longer than the light emission time can be secured with a control margin. Is input from the control calculation unit 120 as V1 and V2 longer than V0.

  The exposure frame period is set to be as short as possible according to the light emission time by adjusting the period of the vertical synchronization signal (exposure frame period) according to the light emission amount of the strobe light = the light emission time. That is, in FIG. 4, the period V2 of the vertical synchronizing signal is made longer than the period V1 of the vertical synchronizing signal in FIG. For this reason, it is possible to minimize frame rate drop due to strobe irradiation.

  FIG. 5 shows a timing chart in which the control according to claims 1 to 3 of the present invention is performed. Here, by operating the shutter button once, two consecutive shootings during focus bracket shooting for shooting a plurality of images are extracted and written in a timing chart. The drive state is described. That is, the lens 101 is moved at the time of focus bracket shooting in which a plurality of images are continuously captured while the lens 101 is intermittently moved and the strobe unit 127 is continuously emitted to emit strobe light as illumination light. The readout frame period of the CMOS image sensor 104 is changed in accordance with the moved position. Here, changing the readout frame period of the CMOS image sensor 104 refers to the period V1 (exposure frame period) of the vertical synchronization signal so as to change the exposure common times t1 and t2 of all the rows of the CMOS image sensor 104. It is to make it longer than V0. This is because the amount of light from the strobe unit 127 depends on the focus position (the position of the lens 101), and the amount of light emission is increased (= light emission time is increased) as the focus position is farther.

  In this embodiment, the focus bracket shooting is exemplified by shooting while moving the focus of the lens 101 from the near side to the far side. Since the movement of the lens 101 requires a mechanical drive time of the focus mechanism 105, the shooting frame is set to once every two frames, and the focus is set to the far side during the period in which the exposure time for shooting is avoided as shown in the figure. Has been moved to. Further, since the farther the photographing position is, the more the amount of light emitted from the strobe unit 127 is required, the light emission time when the focal distance is short is X1, and the light emission time when the focal distance is long is X2. The light emission time by the flash unit 127 is controlled so that X1 <X. For this reason, as in FIGS. 3 and 4, the exposure common time t1 <exposure common time t2, and the period of the vertical synchronization signal is V0 <V1 <V2.

  That is, at the time of focus bracket shooting, the period V2 (exposure frame period) of the vertical synchronization signal at the time of shooting at the far-side focus position is longer than the period V1 (exposure frame period) of the vertical synchronization signal at the time of shooting at the near side. Control is performed so that the light emission time X2 is longer (V1 <V2) and the light emission time X2 is longer than the light emission time X1 so that the light emission amount of the illumination light from the strobe unit 127 is increased.

As a result, even with continuous flash photography, it is possible to achieve strobe photography with optimal exposure conditions corresponding to the focal lengths of focus bracket photography, which captures multiple images in succession, and to increase the speed of photography. Become. Such control functions particularly effectively when executed at the time of focus bracket shooting at the time of macro shooting, which is more susceptible to light intensity than focus bracket shooting at the telephoto shooting side.
Note that although focus bracket shooting has been described here, the same effect can be obtained by performing similar control in so-called strobe AE bracket shooting.

  FIG. 6 shows a timing chart of the control according to claim 6 of the present invention. This chart describes the control at the time of pre-emission by the strobe unit 127. When shooting with a strobe for still images, image quality is important, so uniformity of exposure within one screen is important. However, since the required level of display image quality when displaying through images is lower than that for still images, non-uniformity is reduced. Allowed.

  Therefore, the flash unit 127 is controlled so that light control in the center area in the vertical direction of the screen can be performed, and the flash is pre-flashed on a line near the center without changing the frame rate.

  In FIG. 6, m line is a horizontal line (line near the center without changing the frame rate) located at the center of the recording area (or effective pixel area), and has a relationship of N = 2m or N = 2m-1. . In the exposure frame that emits light according to this control, the period of the vertical synchronization signal (exposure frame period) is set to V3> V0 in order to secure the exposure common time t3 as in FIG.

  In contrast, in the pre-flash frame, the period of the vertical synchronization signal (exposure frame period) is V0, and light emission is performed in a state where there is no exposure common time. However, since strobe light emission is performed in the relationship of δ1> α and δ2> β, dimming by pre-light emission from a line near the center of the screen is possible. With such control, it is possible to perform light control at the time of photographing with simple control without reducing the frame rate at the time of pre-emission.

It is a block diagram which shows the example of 1 structure of the imaging device which concerns on this invention. It is a timing chart before changing the period of the conventional vertical synchronizing signal. It is a timing chart when the exposure frame period is longer than the readout frame period. It is a timing chart at the time of adjusting an exposure frame period according to the light emission time of illumination light. When continuously illuminating illumination light from the illuminating unit while moving the optical element intermittently to capture multiple images, the readout frame period of the imaging element is changed according to the position of the optical element. It is a timing chart in the case of. It is a timing chart when irradiating illumination light from an irradiation unit in advance.

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Optical element 104 Image pick-up element 107 Image pick-up optical system 110 Image processing part 126,128 Memory | storage part 127 Illumination part t0-t3 Exposure common time V0 Reading frame period V1-V3 Exposure frame period X0-X3 Light emission time

Claims (6)

An illumination unit that irradiates light, a photographing optical system that forms a subject image, and a subject image formed by the photographing optical system by each pixel signal that is two-dimensionally arrayed is converted into an electrical signal, and the electrical signal is converted to XY In an imaging apparatus having an imaging device that outputs an address method, an image processing unit that converts an output of the imaging device into a predetermined format, and a storage unit that stores a signal processed by the image processing unit,
Exposure means that starts exposure by resetting the image sensor in units of rows and ends exposure by reading out pixel signals;
In the case where a plurality of images are continuously captured while intermittently moving some optical elements of the photographing optical system and continuously illuminating illumination light from the illumination unit, An imaging apparatus, wherein a readout frame period of the imaging element is changed according to a position. The imaging device according to claim 1,
Changing the readout frame period of the image sensor is to make the exposure frame period longer than the readout frame period in order to change the exposure common time of all the rows of the image sensor. The imaging apparatus according to claim 1 or 2,
When taking a plurality of images continuously while intermittently moving some optical elements of the photographing optical system and continuously irradiating illumination light from the illumination unit, a far-side focus position An image pickup apparatus characterized in that the exposure frame period is lengthened and the light emission amount of the illumination light from the illumination unit is increased as the image is taken. The imaging apparatus according to claim 1, 2, or 3,
When imaging is performed by irradiating illumination light from the illumination unit, the exposure frame period is adjusted in accordance with the emission time of illumination light in order to match the exposure common time of all rows of the image sensor. apparatus. An illumination unit that irradiates light, a photographing optical system that forms a subject image, and a subject image formed by the photographing optical system by each pixel signal that is two-dimensionally arrayed is converted into an electrical signal, and the electrical signal is converted to XY In an imaging apparatus having an imaging device that outputs an address method, an image processing unit that converts an output of the imaging device into a predetermined format, and a storage unit that stores a signal processed by the image processing unit,
Exposure means that starts exposure by resetting the image sensor in units of rows and ends exposure by reading out pixel signals;
An image pickup apparatus, wherein when photographing is performed by irradiating illumination light from the illumination unit, an exposure frame period is made longer than a read frame period so as to lengthen an exposure common time of all rows of the image sensor. The imaging device according to claim 1,
When pre-irradiating illumination light from the illuminator for dimming before still image shooting, the dimming frame period is the same as the normal shooting frame period, and the exposure of the line corresponding to the center in the recorded image coordinates of the image sensor An imaging device which irradiates during a period.

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