JP2005117250A - Imaging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exposure control technology realizing also proper selection of exposure control by an electronic shutter function or of exposure control by a mechanical shutter from the standpoint of suppressing the occurrence of smear. <P>SOLUTION: When an exposure control mode is set to a non-smear priority mode, first a program chart corresponding to the exposure control for selectively carrying out either of the first exposure control using the mechanical shutter and the second exposure control using the electronic shutter function is set. However, when a state of possible occurrence of smear is detected and an exposure control variable for carrying out the second exposure control on the basis of the program chart having already been set is calculated, the program chart for the exposure control is changed into the program chart exclusively used for the first exposure control. Then the exposure control variable is again calculated and set. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an exposure control technique in an imaging apparatus.

  In recent years, the miniaturization of digital camera bodies has progressed, and CCD image sensors (hereinafter abbreviated as “CCD”) used in digital cameras tend to be smaller and have a higher number of pixels. In particular, in the progressive type CCD, since the light shielding film of the vertical transfer CCD becomes extremely fine, the light shielding of the vertical transfer CCD becomes insufficient, and unnecessary charge flows into the vertical transfer CCD even if the exposure is terminated by the electronic shutter function. This causes the occurrence of so-called smear.

  In order to prevent the occurrence of such smear, light shielding by a mechanical shutter (hereinafter abbreviated as “mechanical shutter”) is required. However, since the mechanical shutter requires a certain amount of operation time for opening and closing, a high shutter speed cannot be realized only with the mechanical shutter. Therefore, when the mechanical shutter and electronic shutter function are used together, the electronic shutter function is used when the shutter speed is high, the mechanical shutter is used when the shutter speed is low, and the shutter speed is intermediate between the high speed and low speed. There has been proposed a digital camera that controls exposure time by selectively using either an electronic shutter function or a mechanical shutter (for example, Patent Document 1).

  Prior art documents relating to such technology include the following.

Japanese Patent Laid-Open No. 2002-176588

  In the technique proposed in the above background art, when the shutter speed is intermediate between high speed and low speed, exposure control by the electronic shutter function and exposure control by the mechanical shutter are selectively performed in consideration of operability and the like. However, from the viewpoint of suppressing the occurrence of smear, the point of selectively performing the exposure control by the electronic shutter function and the exposure control by the mechanical shutter is not taken into consideration.

  The present invention has been made in view of the above problems, and provides an exposure control technique capable of appropriately selecting exposure control by an electronic shutter function and exposure control by a mechanical shutter from the viewpoint of suppressing occurrence of smear. The purpose is to do.

  In order to solve the above problems, the invention of claim 1 is a mechanical shutter that controls exposure time by blocking and opening an optical path from a subject, and an electronic shutter that controls exposure time by controlling an electrical state of an image sensor. An image acquisition device that performs exposure control using a function, an image acquisition unit that acquires an image based on an optical image related to the subject, and an image acquisition unit that acquires the image based on the optical image related to the subject Detecting means for detecting a smearable state in which smear may occur in the recorded image to be recorded; and when the smearable state is detected by the detecting means, the mechanical shutter is used forcibly. And a control means for performing exposure control.

  The invention according to claim 2 is the imaging apparatus according to claim 1, further comprising instruction means for instructing start of a shooting preparation operation based on a user operation, wherein the detection means includes the image acquisition. In response to an instruction to start the shooting preparation operation by the instruction unit, the smear is generated in the image acquired by the image acquisition unit before the actual shooting for acquiring the captured image by the unit. It is detected as a possible state.

  The invention according to claim 3 is the imaging apparatus according to claim 1 or 2, wherein the detection unit obtains a pixel value equal to or greater than a predetermined value in an image acquired by the image acquisition unit. A state in which the high-luminance pixels are in a predetermined arrangement state is detected as the smearable state.

  According to a fourth aspect of the present invention, in the imaging apparatus according to the first aspect, the detection unit detects a state in which the subject includes a part having a predetermined luminance or more as the smearable state. It is characterized by that.

  According to a fifth aspect of the present invention, there is provided the imaging apparatus according to any one of the first to fourth aspects, wherein the imaging element is a progressive type CCD.

  The invention according to claim 6 is the imaging apparatus according to any one of claims 1 to 5, wherein the control means does not detect the smearable state by the detection means. Includes performing second exposure control using the electronic shutter function.

  In the present specification, synonymous with “short exposure time” and “fast shutter speed (high speed)”, “long exposure time” and “slow shutter speed (low speed)” Use them appropriately. In addition, “shutter speed value” is used as a term representing the shutter speed as a temporal quantitative value. That is, a large shutter speed value means that the exposure time is long (the shutter speed is slow), and a small shutter speed value means that the exposure time is short (the shutter speed is fast). To do.

  According to the first aspect of the present invention, when a state in which smear can occur is detected, exposure control using the mechanical shutter is forcibly performed, so that the occurrence of smear can be suppressed. Therefore, from the viewpoint of suppressing the occurrence of smear, it is possible to appropriately select the exposure control by the electronic shutter function and the exposure control by the mechanical shutter.

  In addition, according to the second aspect of the present invention, the main image is acquired before the main photographing in response to the instruction to start the photographing preparatory operation based on the user's operation before the main photographing for obtaining the recorded image for recording. Therefore, it is possible to recognize whether or not smear is generated in the recording image for recording before the main photographing.

  According to the third aspect of the present invention, since the state in which the high luminance pixels are in a predetermined arrangement state in the image related to the subject is detected as a state in which smear can occur, a state in which smear can easily occur Or not.

  According to the fourth aspect of the present invention, there is a light source that generates a smear such as the sun in the subject in order to detect a state where a very bright portion is included in the subject as a state where smear can occur. By detecting whether or not it is, it is possible to easily recognize whether or not smear can occur.

  According to the invention described in claim 5, since a progressive type CCD is used as an image pickup device, a high-quality shot image based on all pixels of the image pickup device is obtained by shooting at a high shutter speed using a mechanical shutter. Can be acquired.

  According to the sixth aspect of the present invention, when the state where smear can be generated is not detected, the exposure control using the electronic shutter function is performed. it can.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<1. Configuration of main part of imaging apparatus>
FIG. 1 is a diagram illustrating a main configuration of an imaging apparatus 1 according to an embodiment of the present invention. Here, FIGS. 1A to 1C correspond to a front view, a rear view, and a top view of the imaging apparatus 1, respectively.

  The imaging device 1 is configured as a digital camera, and includes a photographing lens 10 on the front surface thereof.

  In addition, the imaging apparatus 1 is provided with a shooting mode switch 12, a shutter button 13, and an exposure control mode switch 14 on the top surface.

  The shooting mode switch 12 selectively switches between a shooting mode (REC mode) for capturing and recording a subject and a playback mode (PLAY mode) for reproducing an image recorded on the memory card 9 (see FIG. 2). It is a switch for.

  The exposure control mode changeover switch 14 is an exposure control mode (aperture priority mode) that prioritizes the setting of the aperture value, an exposure control mode (shutter speed priority mode) that prioritizes the setting of the shutter speed, and an exposure control mode that suppresses the occurrence of smear. (Smearless priority mode), exposure control mode (manual mode) in which the user arbitrarily sets the shutter speed, aperture value, etc., and exposure control mode (program mode) in which exposure control is performed according to a predetermined program This is a switch for selecting and setting the exposure control mode.

  The shutter button 13 is a two-stage switch that can detect a half-pressed state (S1 on state) and a fully depressed state (S2 on state). When the shutter button 13 is half-pressed in the above photographing mode, the focus / zoom motor driver 47 (see FIG. 2) is driven to perform an autofocus (AF) operation for moving the photographing lens 10 to the in-focus position. . In addition, when the S1 is turned on, automatic exposure control (AE) and white balance (WB) correction operations described later are started.

  On the other hand, when the shutter button 13 is fully pressed in the shooting mode, a main shooting operation (that is, a shooting operation for recording) is performed. In the actual photographing operation, exposure control according to the exposure control mode set by the exposure control mode switch 14 is performed. Therefore, the shutter button 13 instructs the start of the AF operation, AE, and WB correction operation included in the preparation operation for the actual shooting (hereinafter referred to as “shooting preparation operation”) based on the user's pressing operation. .

  An LCD (Liquid Crystal Display) monitor 42 that displays captured images, an optical finder 43, and a frame advance / zoom switch 15 are provided on the rear surface of the imaging apparatus 1.

  The frame advance / zoom switch 15 is composed of four buttons, and is a switch for instructing frame advance of a recorded image in playback mode and zooming at the time of shooting. When the frame advance / zoom switch 15 is set to the shooting mode and the exposure control mode is set to the aperture priority mode, the shutter speed priority mode, or the like, the aperture value to be prioritized or It also functions as a switch that can switch and set the shutter speed.

<2. Functional configuration of imaging apparatus>
FIG. 2 is a block diagram illustrating a functional configuration of the imaging apparatus 1.

  The imaging device 1 includes an imaging sensor 16, a signal processing unit 2 connected to the imaging sensor 16 so as to be able to transmit data, an image processing unit 3 connected to the signal processing unit 2, and a camera control unit 40 connected to the image processing unit 3. And.

  The imaging sensor 16 is configured as an area sensor (CCD imaging device) having a single-plate pixel arrangement in which R (red), G (green), and B (blue) primary color transmission filters are arranged in a checkered pattern. The imaging sensor 16 is an all-pixel readout type (progressive type) CCD imaging device (hereinafter abbreviated as “CCD”), and controls the exposure time by controlling the electrical state of the CCD. It has an electronic shutter function.

  In this image sensor 16, light from the subject is converted into signal charge and accumulated, and in response to the sensor gate pulse, this signal charge is shifted to a vertical charge transfer path (vertical transfer CCD) in the image sensor 16. The data is transferred by a vertical transfer CCD (V-CCD) and a horizontal charge transfer path (horizontal transfer CCD), read out through a buffer, and output.

  In this image sensor 16, an electronic shutter is driven by discharging the accumulated signal charge to the n substrate (hereinafter referred to as “overflow drain drive”) and shifting the signal charge to the V-CCD in response to the sensor gate pulse. Exposure control by function is realized. A pulse for discharging signal charges to the n substrate is hereinafter referred to as an “electronic shutter clear pulse”.

  The image sensor 16 has a transfer mode (high-speed transfer mode, normal transfer mode, low-speed transfer mode) in which the transfer rate of signal charges from the V-CCD to the horizontal transfer CCD (H-CCD) is changed in three stages. doing. Here, for example, when the transfer rate in the normal transfer mode is used as a reference, the transfer rate in the high-speed transfer mode is 8 times and the transfer rate in the low-speed transfer mode is 1/4.

  In addition, the imaging sensor 16 is configured to read out an image signal for all pixel arrays during actual shooting (hereinafter referred to as “all-pixel reading mode”) and all pixels during live view display in a shooting standby state. A mode (hereinafter referred to as “monitoring mode”) for reading out image signals for pixels that are thinned out by 1/8 in the vertical direction in the array.

  The signal processing unit 2 includes a CDS 21, an AGC 22, and an A / D conversion unit 23.

  The analog image signal acquired and output by the image sensor 16 is sampled by the CDS 21 and noise is removed, and then the analog gain is multiplied by the AGC 22 that functions as an amplifying unit, and sensitivity correction is performed.

  The A / D converter 23 digitizes the analog signal normalized by the AGC 22. The digitally converted image signal is subjected to predetermined image processing by the image processing unit 3 to generate an image file. That is, the imaging sensor 16 and the signal processing unit 2 acquire a digital image signal (image) based on the optical image related to the subject.

  The image processing unit 3 includes a CPU and a memory, and includes a RAW interpolation unit 30, a digital processing unit 3P, and an image compression unit 35. Further, the image processing unit 3 includes a distance measurement calculation unit 36, an OSD unit 37, a video encoder 38, a memory card driver 39, and a smear detection unit 50.

  The digital processing unit 3P includes a pixel interpolation unit 31, a resolution conversion unit 32, a white balance control unit 33, and a gamma correction unit 34.

  The image data input to the image processing unit 3 is written into the image memory 41 in synchronization with the reading of the imaging sensor 16. Thereafter, the image data stored in the image memory 41 is accessed, and various processes are performed in the image processing unit 3.

  The image data in the image memory 41 is obtained by masking each RGB pixel with the respective filter pattern by the RAW interpolation unit 30 and the pixel interpolation unit 31, and for the G pixel, a median (intermediate value) filter is used to obtain an intermediate 2 of the surrounding 4 pixels. Replace with the average value. Further, average interpolation is performed for the R pixel and the B pixel.

  In the pixel-interpolated image data, the white balance control unit 33 independently performs gain correction on each of the RGB pixels, and RGB white balance (WB) correction is performed. In this WB correction, a portion that is originally white from a photographic subject is estimated from luminance, saturation data, and the like, and an average value, a G / R ratio, and a G / B ratio of each of R, G, and B are obtained. This is implemented by setting gains for R and B based on these pieces of information.

  The white balance corrected image data is subjected to non-linear conversion suitable for each output device by the gamma correction unit 34, specifically, gamma correction and offset adjustment, and stored in the image memory 41.

  The Y (G color brightness), RY (R color brightness), and BY (B color brightness) data stored in the image memory 41 are set to the number of pixels set by the resolution conversion unit 32. Horizontal or vertical reduction or thinning is performed, and after compression processing by the image compression unit 35, the data is recorded on the memory card 9 attached to the memory card driver 39. At the time of this image recording, a photographic image with a designated resolution is recorded, and a screen nail image (VGA) for reproduction display is created and recorded linked to the photographic image. At the time of recording and reproduction, a screen nail image is displayed on the LCD monitor 42, thereby enabling high-speed image display.

  The resolution conversion unit 32 also performs pixel thinning for image display to create a low-resolution image for display on the LCD monitor 42. At the time of preview, a low resolution image of 640 × 240 pixels read out from the image memory 41 is encoded into NTSC / PAL by the video encoder 38, and the image is reproduced on the LCD monitor 42 as a field image.

  The distance measurement calculation unit 36 performs an evaluation value calculation operation for performing contrast-type autofocus (AF) when the shutter button 13 is in a half-pressed state (S1 on state). For example, an evaluation value that is the sum of absolute values of differences regarding adjacent pixels is calculated for the captured image data in the designated area. The lens position of the photographing lens 10 having the highest evaluation value is set as the in-focus position.

  The OSD (on-screen display) unit 37 can generate various characters, symbols, frames, and the like, and can superimpose them on an arbitrary position of the display image. The OSD unit 37 displays various characters, symbols, frames, and the like on the LCD monitor 42 as necessary.

  The smear detection unit 50 detects a smear occurrence state (hereinafter referred to as “smear occurrence state”) in an image for live view display (live view image). Here, under shooting conditions in which smear occurs in a live view image, smear may occur in a recording image for recording by actual shooting if the exposure time is controlled by the electronic shutter function while the lens shutter 44a is opened. It can be regarded as having high nature. Therefore, the smear detection unit 50 can detect a smear occurrence possible state by detecting a smear occurrence state in the live view image based on the optical image related to the subject. That is, the smear detection unit 50 detects a state in which smear can occur in the recorded image for recording (hereinafter referred to as “smear generation possible state”) based on the optical image of the subject. The detection of the smearable state will be described in detail later.

  The camera control unit 40 includes a CPU and a memory, and processes an operation input performed by the photographer with respect to the camera operation switch 49 including the above-described shooting mode changeover switch 12, shutter button 13, exposure control mode changeover switch 14, and the like. For example, the camera control unit 40 switches to a shooting mode or a playback mode in which a subject is imaged and the image data is recorded by operating the shooting mode switching switch 12 by the photographer.

  Further, the camera control unit 40 sets an exposure control mode for realizing desired exposure control by operating the exposure control mode changeover switch 14, and performs exposure control based on a corresponding program diagram for exposure control. Do. The exposure control program diagram is stored in a nonvolatile memory (not shown) in the camera control unit 40 or the like.

  In the imaging apparatus 1, zoom control and focus control are controlled by the focus / zoom motor driver 47 during preview display (live view display) in which the subject is displayed on the LCD monitor 42 in a moving image manner in the shooting preparation state before the main shooting. .

  The imaging device 1 also has a mechanical shutter (here, a lens) that controls the shutter speed value (exposure time) by changing the blocking and opening states of the optical path on the optical path of light emitted from the subject in the photographing lens 10. It has a shutter 44a).

  Further, an optical aperture (hereinafter simply referred to as “aperture”) 44b is provided at a position adjacent to the lens shutter 44a. When the exposure time is controlled by the lens shutter 44a, the degree of opening of the aperture 44b is controlled based on the shutter speed and aperture value calculated by the camera control unit 40, and the optical path through the lens shutter 44a is controlled. The operation of driving from the opened state (open state) to the state (closed state) for blocking the optical path is controlled. The aperture value of the aperture 44b can be changed from F2.8 to F11. In live view display, as a general rule, the aperture 44b is fixed open (aperture value F2.8) by the shutter / aperture driver 45. The photographing lens 10 is composed of a plurality of lens groups, and is set so that the focal length can be changed by changing the interval between the lens groups.

  Furthermore, the camera control unit 40 has an exposure control unit for performing AE at the time of actual photographing, and performs multi-division photometry on the live view image acquired by the imaging sensor 16, etc. An exposure control unit calculates exposure control data. The exposure control data is information relating to the brightness of the subject, and is calculated as, for example, an exposure value EV based on the settings of the so-called subject brightness value BV and sensitivity SV. Then, under the control of the camera control unit 40, the charge of the image sensor 16 corresponding to the shutter speed at the time of actual photographing is calculated based on the calculated exposure control data and the program diagram corresponding to each set exposure control mode. Exposure control values such as accumulation time (exposure time), aperture value, and analog gain are controlled. That is, the exposure control unit in the camera control unit 40 performs exposure control.

  Specifically, the timing generator sensor driver is set so that the operation timing of the electronic shutter function in the image sensor 16, the exposure time determined by the opening time of the lens shutter 44a, and the aperture value adjusted by the aperture 44b are appropriate. 46 and feedback control for the shutter / aperture driver 45 is performed.

  Even during live view display, the camera control unit 40 calculates exposure control data based on sequentially obtained live view images, and the charge accumulation time of the image sensor 16 so that the live view image maintains an appropriate contrast. Are appropriately changed and controlled.

  When the smear-free priority mode (hereinafter referred to as “SFP mode”) is set, the camera control unit 40 responds to the detection of the smearable state by the smear detection unit 50, and here, the mechanical shutter (here, Exposure control (hereinafter referred to as “first exposure control”) is performed in which the lens shutter 44a) is forcibly used to control the exposure time. That is, when the smear detection state is detected by the smear detection unit 50, the camera control unit 40 performs the first exposure control using the mechanical shutter forcibly.

  On the other hand, when the smear detection state is not detected by the smear detection unit 50, the first exposure control using the mechanical shutter is simply performed in the low shutter speed range, and the electronic shutter function is used in the high shutter speed range. Exposure control for controlling the exposure time (hereinafter referred to as “second exposure control”) is performed. The program diagram and exposure control operation corresponding to the SFP mode will be described in detail later.

<3. Smear generation suppression method>
In the imaging apparatus 1, the second exposure control is performed when the shutter speed is relatively high, and the first exposure control is performed when the shutter speed is relatively low. Note that the opening and closing of the lens shutter 44a requires a time required for the mechanical opening / closing operation itself, a time lag from when the control signal is received to the start of driving, and a certain amount of time for the actual operation. And if you try to realize a high-speed shutter mechanically, the cost will inevitably increase. Therefore, when the exposure time is shorter than 1/1000 second, the second exposure control by the electronic shutter function is performed, and when the exposure time is 1/1000 second or more, the first exposure control by the lens shutter is performed. .

  Here, since light shielding by the mechanical shutter is effective in a state where smear can occur, it is preferable to control the exposure time using the mechanical shutter, and in a state where smear does not occur, the luminance of the subject is high. If it is high to some extent, it is preferable to control the exposure time to be short by using an electronic shutter function in order to avoid the occurrence of blurring or blurring in the captured image due to the movement of the subject or camera shake.

  Therefore, the imaging apparatus 1 according to the present embodiment has an SFP mode in which exposure control is changed according to the detection result of the smearable state.

  Hereinafter, the exposure control timing by the electronic shutter function and the lens shutter 44a will be described including the driving of the imaging sensor 16, and then the program diagram corresponding to the SFP mode and the shooting operation in the SFP mode will be described.

<3-1. Exposure control timing>
FIG. 3 is a timing chart showing driving of the image sensor 16 and the lens shutter 44a during exposure control by the electronic shutter function. FIG. 4 is a timing chart showing driving of the image sensor 16 and the lens shutter 44a during exposure control by the mechanical shutter (here, the lens shutter 44a).

  3 and 4, from the top, the vertical synchronizing signal (VD), the horizontal synchronizing signal (HD), the signal charge accumulation state, the V-CCD transfer mode, the sensor gate pulse, the open / close state of the lens shutter 44a, and the electronic shutter clear. The pulse timing is shown.

  First, the second exposure control by the electronic shutter function will be described. Here, since exposure control is performed by the electronic shutter function, the lens shutter 44a is in an open state from the live view display state to the end of the main photographing.

  As shown in FIG. 3, first, the accumulation of the signal charge for live view immediately before the start of the main photographing is finished, and the signal charge accumulated in response to the sensor gate pulse is shifted to the V-CCD (time t1). . The shifted signal charges are transferred in the normal transfer mode in the V-CCD, and unnecessary charges in the V-CCD are discharged in the high-speed transfer mode from the exposure (main exposure) before the main photographing to the end of the main exposure. The main exposure is started by the electronic shutter clear pulse (time t2), and the accumulated signal charge is shifted to the V-CCD in response to the sensor gate pulse, thereby completing the main exposure (time t3). Then, in response to the sensor gate pulse, a lens shutter control signal is issued, and after a lapse of time due to a slight drive delay, the lens shutter 44a starts driving from the open state to the closed state (time t4), and the closed state (Time t5).

  As described above, the exposure time of the main exposure is from the last electronic shutter clear pulse to the generation timing of the sensor gate pulse, and the shutter is accurately released by the electronic shutter function, and a high shutter speed, that is, a short exposure is possible. . However, in the exposure control by the electronic shutter function, unnecessary charges flow into the V-CCD during the main exposure or after the main exposure is completed until the lens shutter 44a is closed, which causes so-called smear.

  Next, the first exposure control by the lens shutter 44a will be described.

  As shown in FIG. 4, the main exposure is started by the electronic shutter clear pulse when the lens shutter 44a is open (time t10), and signal charges are accumulated. Then, the main exposure is completed when the lens shutter 44a is changed from the open state to the closed state in accordance with the shutter speed calculated in advance (time t11). In the high-speed transfer mode, after unnecessary charges generated in the V-CCD are completely discharged, the signal charges accumulated in the V-CCD are shifted in response to the sensor gate pulse (time t12). The signal charge is read from the image sensor 16.

  As described above, in the exposure control by the lens shutter 44a, after the lens shutter 44a is completely closed, unnecessary charges in the V-CCD are completely discharged, and then the signal charges by the main exposure are read. That is, after the camera control unit 40 completes blocking of the optical path by the lens shutter 44a and before transferring the signal charge accumulated in the imaging sensor 16 by the V-CCD, unnecessary signal charge in the V-CCD is transferred. Control to eliminate. As a result, it is possible to suppress and prevent the occurrence of smear and obtain a high-quality captured image. However, due to the time required to open and close the lens shutter 44a, a high shutter speed cannot be realized by exposure control using the lens shutter 44a.

<3-2. Program diagram corresponding to priority mode without smear (SFP mode)>
In the SFP mode, in order to suppress and prevent the occurrence of smear, first exposure control using the lens shutter 44a is performed in a state where smear can occur regardless of the brightness value of the subject, that is, the exposure value EV. That is, the program diagram for exposure control is appropriately changed according to whether or not a smearable state is detected.

  Here, first, an exposure control program diagram corresponding to the SFP mode for suppressing the occurrence of smear will be described, and the change of the program diagram will be further described later.

  FIG. 5 is a diagram illustrating a program diagram corresponding to the SFP mode. FIG. 5A shows a program diagram used when a smearable state is not detected, and FIG. 5B shows a program diagram used when a smearable state is detected. Yes. In the program diagram shown in FIG. 5, the vertical axis represents the aperture value (F), the horizontal axis represents the shutter speed value (SS), and the oblique axis represents the exposure value (EV). In the program diagrams in FIG. 5 and subsequent figures, the bold line shows the program diagram corresponding to the first exposure control using the lens shutter 44a, and the thick broken line shows the second exposure control using the electronic shutter function. The corresponding program diagram is shown.

  For example, if the smearable state is not detected, as shown in FIG. 5A, the first exposure control is performed with the shutter speed value ≧ 1/1000 seconds, and the shutter speed value <1/1000 seconds. 2 exposure control is performed. Specifically, when the exposure value EV ≦ 10, the first exposure control is performed in which the shutter speed value is simply decreased while the aperture value F2.8 remains fixed as the exposure value EV increases. When 10 <exposure value EV ≦ 16, as the exposure value EV increases, the aperture value is changed from F2.8 to F8, and the shutter speed value is decreased from 1/125 seconds to 1/1000 seconds. Perform exposure control. If 16 <exposure value EV ≦ 18, the aperture value is changed from F8 to F11 as the exposure value EV increases, and the shutter speed value is decreased from 1/1000 second to 1/2000 second. Perform exposure control. Further, when the exposure value EV> 18, second exposure control is performed in which the shutter speed value is simply decreased while the aperture value F11 remains fixed as the exposure value EV increases.

  On the other hand, when the smearable state is detected, as shown in FIG. 5B, the first shutter speed value is 1/1000 second or less in order to suppress / prevent smearing. Perform exposure control. Specifically, the exposure value EV ≦ 16 is the same as the program diagram shown in FIG. On the other hand, when 16 <exposure value EV ≦ 17, first exposure control is performed in which the aperture value is changed from F8 to F11 while the shutter speed value is fixed at 1/1000 second. In addition, when the exposure value EV> 17, the aperture cannot be reduced more than F11. Therefore, although not shown in FIG. 5B, the aperture value F11 and the shutter speed value = 1 as the exposure value EV increases. The first exposure control is performed to reduce the analog gain while maintaining / 1000 seconds. That is, when the exposure value EV further decreases from the point GCP in FIG. 5B, appropriate exposure is obtained by reducing the analog gain. That is, the program diagram shown in FIG. 5B can be referred to as a “program diagram dedicated to the first exposure control” because it shows exposure control by only the first exposure control.

<3-3. Detection of smear possible state>
Hereinafter, an operation in which the smear detection unit 50 detects a smear occurrence state in which a smear can occur in the captured image by detecting a smear occurrence state in the live view image will be described.

  FIG. 6 is a diagram illustrating a method for detecting a smearable state. 6A shows an evening scene including the sun SU having a very high luminance, and FIG. 6B shows the relationship between the optical image of the subject irradiated on the image sensor 16 and the smear SM. FIG. 6C shows a live view image in which smear SM is generated. Note that, as shown in FIG. 6B, an optical image in which the subject is inverted is formed on the image sensor 16. In FIGS. 6B and 6C, the portion corresponding to the sun SU in the optical image and the image is shown as the sun SU.

  When the lens shutter 44a is in the open state, for example, when shooting a sunset scene including the sun SU having a very high luminance as shown in FIG. 6A, as shown in FIG. 6B, the sun SU Unnecessary charges are generated at the position where the optical image is formed, and unnecessary charges are transferred from the position toward the H-CCD, that is, in the vertical direction along the V-CCD. When the live view image is acquired, the lens shutter 44a is always in the open state. Therefore, as shown in FIG. 6C, the live view image has a vertical direction (V-CCD) from the position of the sun SU. Smear SM extending long in the direction along the line).

  In this way, when the subject includes a portion with extremely high luminance, smear occurs in the live view image. Then, the smear detection unit 50 detects a smear occurrence state in the live view image as a smear occurrence possible state.

  Specifically, for example, in a live view image, a pixel (high luminance pixel) having a pixel value equal to or higher than a predetermined value (for example, luminance is 8 bits, that is, predetermined value = 250 when expressed in 0 to 255 gradations). However, if a linear portion (hereinafter referred to as “linear high-intensity portion”) along the direction corresponding to the charge transfer direction in the V-CCD of the image sensor 16 is formed, smear occurs in the live view image. The state can be detected. In other words, in the live view image, a state in which high-luminance pixels having a pixel value equal to or larger than a predetermined value are in a predetermined arrangement state (a state in which the high-luminance pixels are arranged linearly along a direction corresponding to the charge transfer direction of the V-CCD) Is detected as a smearable state.

<3-4. Shooting Operation Flow in Smearless Priority Mode (SFP Mode)>
FIG. 7 is a flowchart illustrating an imaging operation flow in the SFP mode. This operation flow is mainly controlled by the camera control unit 40. When the SFP mode is selected as the exposure control mode and the REC mode is set, or when the SFP mode is selected as the exposure control mode and the REC mode is set, the shooting operation flow in the SFP mode is started. Then, the process proceeds to step S1 in FIG.

  In step S1, the exposure control mode is set to the SFP mode, and the process proceeds to step S2. Here, first, a program diagram shown in FIG. 5A is set as a program diagram for exposure control.

  In step S2, live view display is started, and the process proceeds to step S3.

  In step S3, it is determined whether or not the shutter button 13 is half-pressed and the S1 is on. Here, if the S1 is on, the process proceeds to step S4, and the determination operation of step S3 is repeated until the S1 is on.

  In step S4, in response to the S1 being turned on, AF and WB operations are performed, and a photometric operation for the live view image included in the AE is started, and the process proceeds to step S5. Here, when the photometric operation is started, exposure control data is calculated and exposure control values (shutter speed value, aperture value, etc.) are calculated and set based on the program diagram set in step S1. Done.

  In step S5, a smear occurrence state detection operation is performed, and the process proceeds to step S6. Here, as described above, the smear detection unit 50 detects a linear high-luminance part in the live view image, thereby detecting a smear occurrence state (that is, a smear possible state) in the live view image. That is, in the main operation flow, when the S1 is turned on in response to an instruction to start the shooting preparation operation based on the pressing operation of the shutter button 13 by the user before the main shooting, the smear generation state in the live view image is generated. Detect as possible state. In other words, in response to the start of the shooting preparation operation, a smear occurrence state (that is, a smear occurrence possible state) is detected.

  In step S6, it is determined whether or not a smear occurrence state (that is, a smear possible state) is detected in step S5. Here, if a smear occurrence state is detected in step S5, the process proceeds to step S7, and if not detected, the process proceeds to step S10.

  In step S7, an exposure control value (here, shutter speed value) calculated based on the photometric operation in step S4 is confirmed, and the process proceeds to step S8.

  In step S8, the shutter speed value confirmed in step S7 is a range of shutter speed values in which exposure control can be performed with the lens shutter 44a in the program diagram shown in FIG. 5A (hereinafter referred to as “mechanical shutter control range”). Or not). Here, if the shutter speed value belongs to the mechanical shutter control range, the process proceeds to step S10, and if not, the process proceeds to step S9.

  Here, even if the smear occurrence state is detected, the program shown in FIG. 5A is used if it belongs to the mechanical shutter control range (here, the shutter speed value is a range of 1/1000 second or less). The exposure control value calculated based on the diagram is adopted. However, since the program diagrams shown in FIGS. 5A and 5B are exactly the same when the shutter speed value is 1/1000 seconds or less, here, FIG. This is the same as employing the exposure control value calculated based on the program diagram dedicated to the first exposure control used when the smearable state shown is detected.

  In step S9, the exposure control program diagram is changed to the first exposure control program diagram shown in FIG. 5B, the exposure control value is calculated and set again, and the process proceeds to step S10. Here, the exposure control value is reset based on the exposure control data calculated in step S4 and the program diagram shown in FIG.

  In step S10, it is determined whether or not the shutter button 13 is fully pressed and the S2 is on. Here, if the S2 is on, the process proceeds to step S11. If the S2 is not on, the process returns to step S3.

  In step S11, imaging processing including exposure for actual photographing, image signal readout operation, and the like are performed, and the process proceeds to step S12. Here, the exposure time and the like are controlled based on the exposure control value set in step S4 or step S9.

  In step S12, the recording process of the captured image obtained by the actual shooting is performed, and the process proceeds to step S13. Here, various image processing is performed on the image signal acquired in step S11, and the recorded image is recorded in the memory card 9 as a recording image.

  In step S13, it is determined whether or not there is a next shooting, that is, whether or not the next frame is shot. Here, for example, when the shooting mode changeover switch 12 is operated by the user to switch to the reproduction mode, it is determined that there is no next shooting and the process proceeds to step S14. On the other hand, for example, when the shooting mode is maintained, it is assumed that there is the next shooting, and the process returns to step S2, and the processing from step S2 to step S13 is performed again. Even when the exposure control mode is changed from the SFP mode to another mode, the process proceeds to step S14 on the assumption that there is no next shooting.

  In step S14, processing for ending the shooting operation in the SFP mode is performed, and the shooting operation flow in the SFP mode is ended.

  As described above, in the imaging apparatus 1 according to the present embodiment, when the exposure control mode is set to the smear-less priority mode (SFP mode), first, according to the exposure value EV in the first and second exposure controls. A program diagram corresponding to exposure control for selectively performing the other exposure control is set. However, when the smear detection unit 50 detects a smear-occurrence enabled state and an exposure control value for performing the second exposure control based on the already set program diagram is calculated, The program diagram for exposure control is changed to a program diagram dedicated to the first exposure control. Then, the exposure control value is calculated and set again. That is, the imaging apparatus 1 is controlled to perform the first exposure control using the mechanical shutter forcibly when a state where smear may occur in the captured image is detected. As a result, it is possible to suppress the occurrence of smear in the recorded photographed image, and to appropriately select the exposure control by the electronic shutter function and the exposure control by the mechanical shutter from the viewpoint of suppressing the occurrence of smear.

  Further, before the actual shooting, in response to an instruction to start the shooting preparation operation based on the user's operation, the smear occurrence state in the live view image is detected as a smear possible state. As a result, it is possible to recognize whether or not smear can occur in the recorded image before recording.

  Further, in the live view image related to the subject, a state where the high luminance pixels are in a predetermined arrangement state is detected as a smearable state. Therefore, it is possible to easily recognize whether or not smear can occur in the recorded image for recording.

  Further, when a progressive type CCD image sensor that is prone to smear when the structure is extremely small as the image sensor 16 as in the image pickup apparatus 1, another type of CCD image sensor such as an interlace type is used. Compared to the case, it is possible to significantly suppress the occurrence of smear by adopting the method as described above. Therefore, from the viewpoint of suppressing occurrence of smear, the degree of effectiveness that exposure control by the electronic shutter function and exposure control by the mechanical shutter can be appropriately selected increases.

  For example, in the case of using an interlace type CCD image pickup device such as a two-field readout type in which smear is not easily generated even when the structure of the image sensor 16 is miniaturized, in the exposure control by the electronic shutter function, Only signal charges in the first field that are continuously read out in time can be used. This is because the exposure times of the first field and the second field are different. For this reason, when the above-described method is adopted, a high-quality captured image based on all the pixels of the image sensor 16 can be obtained by using a progressive type CCD image sensor. The number of pixels can be increased, and a more preferable result can be obtained.

<4. Modification>
As mentioned above, although embodiment of this invention was described, this invention is not limited to the thing of the content demonstrated above.

  For example, in the above-described embodiment, the smearable state is detected by detecting the linear high-luminance part in the live view image. However, the present invention is not limited to this. For example, the absolute illuminance (luminance) of the subject The smearable state may be detected based on the above. For example, during live view display, it is possible to detect a smearable state by detecting a subject (high brightness subject) whose spotlight in the night view or the illuminance such as the sun is a predetermined value (for example, BV value 13) or more. Anyway. That is, a state in which the subject includes a portion having a predetermined luminance or more may be detected as a smearable state.

  In this case, by detecting the presence of high-luminance pixels from the live view image, it is possible to detect a state in which the subject includes a portion with a predetermined luminance or higher. A sensor for detecting the presence of a high-luminance subject may be provided. For example, when considering a single-lens reflex digital camera, such a sensor may be a sensor that receives light reflected by a reflecting mirror or the like provided in front of a CCD image sensor and performs multi-segment photometry. It is done.

  In this way, it is possible to detect whether or not a light source that generates smear such as the sun exists in the subject by detecting a state in which the subject includes a very bright portion as a smearable state. it can. As a result, it is possible to easily recognize whether or not smear can occur.

  Further, when at least one of the linear arrangement state of the high-luminance pixels and the high-luminance subject in the live view image is detected, a smearable state may be detected.

  Also, depending on the aperture value during live view display, the illuminance of a high-brightness subject that causes smear changes, so the predetermined value (threshold value) of illuminance for making a high-brightness subject changes according to the change in aperture value. May be changed appropriately.

  Also, in the above-described embodiment, when the smearable state is not detected, the first exposure control using the mechanical shutter is performed at high speed in the low-speed shutter speed range as shown in FIG. In the shutter speed range on the side, the exposure control value is calculated based on a program diagram for performing the second exposure control using the electronic shutter function. However, the present invention is not limited to this. For example, FIG. In the program diagram shown in FIG. 8, the portion corresponding to the first exposure control by the mechanical shutter may be changed to the second exposure control by the electronic shutter function as shown in FIG. That is, when the smear detection state is not detected by the smear detection unit 50, the second exposure control using the electronic shutter function may always be performed. As described above, when a state where smear can be generated is not detected, the exposure control using the electronic shutter function is performed, so that the first exposure control using the mechanical mechanical shutter is performed. In addition, highly accurate exposure control can be performed. Further, as in the first exposure control, after the exposure is completed, the mechanical shutter is closed, and the time required for discharging unnecessary signal charges in the V-CCD is not required. It is possible to shorten the time including the recording of the captured image. As a result, it is possible to quickly move to the next shooting, and continuous shooting with a short interval becomes possible.

  In the above-described embodiment, the smear detection unit 50 detects the smearable state by detecting the linear high luminance portion in the live view image. However, the present invention is not limited to this. When obtaining a view image, if the image signal output from the optical black portion arranged around the effective pixel of the CCD image sensor shows a pixel value greater than or equal to a predetermined value, a smear occurrence state in the live view image, That is, a smearable state may be detected.

  FIG. 9 is a diagram for explaining a method of detecting a smearable state using optical black. FIG. 9 shows an image G based on an image signal read from all pixels of the image sensor 16 during live view display. As shown in FIG. 9, in the image G, when a very high-intensity sun SU is included in the subject, linear smears SM are generated above and below the sun SU. An area OB in which pixels read out from the optical black portion are arranged around an area US corresponding to the effective pixels of the image sensor 16 (that is, an area corresponding to the live view image) US. . In this area OB, pixels that are almost black (pixel value is 0 gradation) are normally arranged. However, in the case where smear SM is generated as shown in FIG. In the sensor 16, since unnecessary charges also flow into the pixels of the optical black portion where an optical image related to the subject is not originally formed, high brightness portions P <b> 1 and P <b> 2 are generated in the region OB. Therefore, even if the smear detection unit 50 detects the high luminance portions P1 and P2, it is possible to detect the smearable state.

  In the above-described embodiment, the smearable state is detected based on the live view image after the S1 is turned on. However, the present invention is not limited to this. For example, the live view before the S1 is turned on is detected. You may make it detect a smear possible state based on an image.

  In the above-described embodiment, when the luminance is expressed by 8 bits, a pixel having a pixel value of 250 gradations or more is a high luminance pixel. However, the present invention is not limited to this. For example, When the luminance is expressed by gradation with 10 bits, a pixel having a pixel value belonging to the upper 1 bit or 2 bits may be a high luminance pixel.

It is a figure which shows the principal part structure of the imaging device which concerns on embodiment of this invention. FIG. 25 is a block diagram illustrating a functional configuration of an imaging apparatus. It is a timing chart about exposure control by an electronic shutter function. It is a timing chart about exposure control by a mechanical shutter. It is a figure which illustrates the program diagram in smearless priority mode. It is a figure explaining the method of detecting a smear possible state. It is a flowchart which shows the imaging | photography operation | movement flow in non-smear priority mode. It is a figure which illustrates the program diagram concerning a modification. It is a figure for demonstrating the detection method of the smear possible state which concerns on a modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Imaging device 2 Signal processing part 3 Image processing part 10 Shooting lens 16 Imaging sensor 40 Camera control part 44a Lens shutter 44b Aperture 50 Smear detection part

Claims (6)

An imaging apparatus that performs exposure control using a mechanical shutter that controls exposure time by blocking and opening an optical path from a subject, and an electronic shutter function that controls exposure time by controlling an electrical state of the imaging element,
Image acquisition means for acquiring an image based on an optical image related to the subject;
Detecting means for detecting a smearable state in which smear may occur in a recorded photographed image acquired by the image acquiring means based on an optical image relating to the subject;
Control means for performing first exposure control forcibly using the mechanical shutter when the smearable state is detected by the detection means;
An imaging apparatus comprising: The imaging apparatus according to claim 1,
Instruction means for instructing the start of the shooting preparation operation based on the user's operation;
With
The detection means is
A state in which smear has occurred in the image acquired by the image acquisition unit in response to an instruction to start the imaging preparation operation by the instruction unit before the actual acquisition of acquiring the captured image by the image acquisition unit Is detected as a smearable state. The imaging apparatus according to claim 1 or 2,
The detection means is
An image pickup apparatus that detects a state in which high luminance pixels having a pixel value equal to or greater than a predetermined value are in a predetermined arrangement state in the image acquired by the image acquisition unit as the smearable state. The imaging apparatus according to claim 1,
The detection means is
An imaging apparatus, wherein a state in which the subject includes a portion having a predetermined luminance or more is detected as the smearable state. The imaging apparatus according to any one of claims 1 to 4,
The image sensor is
An imaging apparatus, which is a progressive type CCD. An imaging apparatus according to any one of claims 1 to 5,
The control means is
An image pickup apparatus that performs second exposure control using the electronic shutter function when the smearable state is not detected by the detection means.

Images