JP4961334B2 - Imaging apparatus and control method thereof - Google Patents

Description

  The present invention relates to an imaging apparatus and a control method thereof, and more particularly to an imaging apparatus represented by a single-lens reflex camera having a live view function and a control method thereof.

  In recent years, a subject image formed by a photographing optical system is photoelectrically converted into an electric signal using an image sensor such as a CCD sensor or a CMOS sensor, and the image signal obtained thereby is recorded on a recording medium or the like. Digital cameras are widely used.

  One of the features of this digital camera is the so-called live view in which the image signal of the subject periodically acquired from the image sensor is sequentially displayed on a liquid crystal monitor provided on the back surface of the digital camera in real time before shooting. There is a function. For example, when shooting using an optical viewfinder, the shooting angle of view cannot be confirmed if the subject is dark, but in live view, it can be checked by changing the brightness of the display on the liquid crystal monitor. Also, in the focus confirmation of the subject, the live view can enlarge and display a portion where the focus is to be confirmed, so that more detailed focus confirmation can be performed compared to the optical viewfinder. For example, a digital single-lens reflex camera equipped with a live view function has been proposed in order to obtain a focus accuracy required for taking astrophotography (see, for example, Patent Document 1).

  In order to perform live view with a digital single-lens reflex camera, the following control is usually performed. First, a quick return mirror (hereinafter referred to as “mirror”) for folding a photographing light beam toward the optical viewfinder in order to observe the subject image with the optical viewfinder is raised. Then, the photographing light flux is taken as a so-called bulb state in which the front curtain of the focal plane shutter (hereinafter referred to as “mechanical shutter”) composed of the front curtain and the rear curtain travels and the rear curtain is held in a state before traveling. Is always in a state where it can be taken into the image sensor. In other words, the valve state must continue throughout the live view.

  Here, the current mainstream shutter is configured so that the front curtain (front blade) and the rear curtain (rear blade) are driven by a spring. First, the front curtain and the rear curtain are energized by a charging member (hereinafter referred to as “ This is referred to as a “charged state”.) It is attracted and held by an electromagnet against the biasing force of the spring. Then, in response to a command to start running the front curtain and the rear curtain, the energization of the electromagnets is stopped in sequence to release the suction hold, and the front curtain and the rear curtain are run sequentially. That is, in order to hold the shutter in the valve state, after the front curtain is run and the shutter is opened, it is necessary to leave the rear curtain in a charged state so that the shutter does not close. It is necessary to continue energizing the electromagnet. If the electromagnet is continuously energized in this way, the temperature of the electromagnet rises to a considerable temperature.

  By the way, when shooting astronomical photographs, if noise (scratches, etc.) occurs in the image sensor, the scratches (also called star noise) are reflected in the screen as if a star is present, May have a significant impact on astrophotography. The temperature increase of the electromagnet of the shutter as described above causes a temperature increase of the image sensor immediately behind the shutter, which causes noise generation.

  Therefore, Patent Document 1 discloses a method for controlling the valve state so as not to continue for a predetermined time. Also disclosed is a method for controlling to stop the valve state when the temperature detecting means for detecting the shutter temperature detects that the shutter temperature exceeds a predetermined reference value. These controls prevent thermal noise from appearing in the screen.

  On the other hand, a method for controlling the shutter speed by driving the front curtain of a so-called electronic shutter that sequentially resets and scans the image sensor and then running the rear curtain of the mechanical shutter when taking a still image in the live view state. It has been known. (For example, refer to Patent Document 2).

Japanese Patent Laid-Open No. 2006-033705 Japanese Patent Laid-Open No. 11-41523

  As described above, the temperature increase of the electromagnet of the shutter during live view is a characteristic such as the time it takes for the trailing curtain to actually travel after the suction holding state is released after the electromagnet is de-energized. This causes a change in the so-called cutting characteristics. Therefore, when still image shooting is performed by the method described in Patent Document 2, there is a problem that shutter accuracy is deteriorated and unevenness of exposure amount (hereinafter referred to as exposure unevenness) occurs. . This problem becomes more significant as the shutter speed becomes higher, and conversely, if the shutter speed is low, the effect becomes smaller.

  With respect to the above problem, Patent Document 1 focuses on astronomical photography, and the shutter speed at the time of photography is a long time such as bulb photography. Evil was not considered.

  Furthermore, the exposure control at the time of still image shooting in Patent Document 1 is based only on the mechanical shutter, and the electronic shutter is not touched at all. In other words, the live view in Patent Document 1 is so-called bulb photography, and there is no mention of taking a still image using an electronic shutter from the live view state.

  Japanese Patent Application Laid-Open No. H10-228688 describes correction of exposure unevenness with respect to a change in curtain shutter speed in still image shooting from a live view state. Further, it also describes correction of exposure unevenness caused by variations in the so-called release time lag, which is the time from when the still image shooting is instructed until the trailing curtain actually starts to travel. However, there is no description of the cutting characteristics.

  The present invention has been made in view of the above problems. In a digital single-lens reflex camera capable of performing live view using a mechanical shutter and an electronic shutter together, uneven exposure in still image shooting is possible regardless of the continuous use time of live view. The purpose is to reduce.

In order to achieve the above object, an imaging apparatus according to the present invention includes an imaging element for photographing a subject, a traveling curtain that travels in a direction that blocks incident light on the imaging element, and the traveling curtain that travels by electromagnetic force. Measured by the mechanical shutter including a curtain holding mechanism that holds the previous initial position, a time measuring unit that measures the energization time of the curtain holding mechanism, and the time measuring unit when a still image shooting is instructed When the energization time is equal to or longer than the predetermined time, the running curtain is run before starting exposure for still image shooting, and after running, the running curtain is held at the initial position by the curtain holding mechanism and then the exposure is started. And a control means .

In order to achieve the above object, an image pickup apparatus control method according to the present invention includes an image pickup device for photographing a subject, a travel curtain that travels in a direction that blocks incident light on the image sensor, and the travel curtain. And a mechanical shutter including a curtain holding mechanism that holds the curtain in an initial position before traveling by electromagnetic force, and a time measurement unit measures the energization time of the curtain holding mechanism. When the energization time measured in the measurement step and the time measurement step when a still image shooting is instructed is a predetermined time or more, the control means travels the running curtain before starting the exposure of the still image shooting. And a control step of starting the exposure after the traveling curtain is held at the initial position by the curtain holding mechanism after traveling .

  According to the present invention, in a single-lens reflex camera capable of displaying a live view using a mechanical shutter and an electronic shutter together, it is possible to reduce uneven exposure in still image shooting regardless of the duration of the live view display. .

  The best mode for carrying out the present invention will be described below in detail with reference to the accompanying drawings. However, the dimensions, shapes, relative arrangements, and the like of the components exemplified in the present embodiment should be changed as appropriate according to the configuration of the apparatus to which the present invention is applied and various conditions. It is not limited to.

<First Embodiment>
A first embodiment of the present invention will be described. FIG. 1 is a schematic sectional view of a digital single-lens reflex camera according to the first embodiment.

  Reference numeral 1 denotes a camera body. Reference numeral 2 denotes a mount for allowing a photographic lens 3 (described later) to be attached to and detached from the camera body 1. The mount includes an interface unit for communicating various signals and supplying drive power. Reference numeral 3 denotes an interchangeable photographic lens, which has a focus lens group, a zoom lens group, and a diaphragm device (not shown) inside. In FIG. 1, each lens group is illustrated with two lenses for convenience, but in actuality, it is configured by a complex combination of lens groups with a large number of lenses.

  Reference numeral 4 denotes a main mirror composed of a half mirror, which can be rotated according to the operating state of the camera. When observing a subject with a finder, the illuminating optical path is inclined, and a light beam from the photographic lens 3 is bent and guided to a finder optical system, which will be described later. The light flux of the subject image to be guided is guided to the image sensor 6 described later.

  Reference numeral 5 denotes a shutter for controlling the incidence of a light beam from the photographic lens 3 to an image sensor 6 to be described later, that is, a shutter for controlling an exposure aperture to the image sensor 6, a front curtain for exposing the image sensor 6, and light shielding And a second curtain. The details of the shutter mechanism will be described later. Reference numeral 6 denotes an image sensor such as a CCD sensor or a CMOS sensor.

  Reference numeral 7 denotes a sub-mirror that rotates together with the main mirror 4 and is composed of a half mirror. The sub-mirror 7 bends the light beam transmitted through the main mirror 4 when the main mirror 4 is obliquely arranged in the photographing optical path, and converts the light beam to the AF sensor 8 (described later) and the light beam transmitted and guided to the image sensor 6 (described later). It is divided.

  Reference numeral 8 denotes an AF sensor, which includes a secondary imaging lens, an area sensor including a plurality of CCDs, and the like, and can detect a focus by a known phase difference method.

  Reference numeral 9 denotes a focusing plate disposed on the primary imaging surface of the photographic lens 3. A Fresnel lens (condenser lens) is provided on the incident surface, and a subject image (finder image) is formed on the exit surface. Reference numeral 10 denotes a finder optical path changing pentaprism, which corrects a subject image formed on the exit surface of the focusing plate 9 into an erect image. Reference numerals 11 and 12 are eyepiece lenses. Here, an optical system including the focus plate 9, the pentaprism 10, and the eyepieces 11 and 12 is referred to as a finder optical system.

  Reference numeral 13 denotes an AE sensor, which is composed of photodiodes corresponding to the respective areas in the multi-divided shooting screen, and measures the luminance of the subject image formed on the exit surface of the focusing screen 9.

  A liquid crystal monitor 14 displays captured images and various types of shooting information.

  Next, the configuration of the shutter 5 will be described. FIG. 2 is a schematic front view of the shutter 5.

  In FIG. 2, reference numeral 51 denotes a shutter base plate having an aperture 51 a that allows a photographing light beam to pass therethrough, and 52 denotes a charge lever for charging a drive spring for driving the shutter 5.

  53 is a front curtain drive lever for driving the front curtain of the shutter 5, and a front curtain drive spring (not shown) is provided on the same rotation axis. 54 is a front curtain armature fixed to the front curtain drive lever 53, 55 is a front curtain armature shaft that fixes the front curtain armature 54 to the front curtain drive lever 53, and 56 is between the front curtain armature shaft 55 and the front curtain drive lever 53. This is a first-curtain absorbing rubber that absorbs shocks. Reference numeral 57 denotes a front curtain yoke that electromagnetically holds the front curtain armature 54, 58 denotes a front curtain coil that generates electromagnetic force in the front curtain yoke 57, and 59 denotes a front curtain bobbin that holds the front curtain coil 58.

  Reference numeral 61 denotes a rear curtain drive lever for driving the rear curtain of the shutter 5, and a rear curtain drive spring (not shown) is provided on the same rotation axis. 62 is a rear curtain armature fixed to the rear curtain drive lever 61, 63 is a rear curtain armature shaft that fixes the rear curtain armature 62 to the rear curtain drive lever 61, and 64 is between the rear curtain armature shaft 63 and the rear curtain drive lever 61. This is a rear-curtain absorbing rubber that absorbs shocks. 65 is a rear curtain yoke that electromagnetically holds the rear curtain armature 62, 66 is a rear curtain coil that generates electromagnetic force in the rear curtain yoke 65, and 67 is a rear curtain bobbin that holds the rear curtain coil 66.

  FIG. 3 is a rear view showing the blades of the shutter 5.

  In FIG. 3, reference numeral 101 denotes a front curtain arm that holds a front blade group that constitutes the front curtain of the shutter 5, and engages with a foot portion 53 a of the front curtain drive lever 53, and rotates in conjunction with the front curtain drive lever 53. It rotates around 101a. Reference numeral 102 denotes a front curtain follower arm that holds the front blade group and rotates around the rotation center 102 a in conjunction with the front curtain arm 101. Reference numerals 103, 104, 105, and 106 are front blades that are held by the front curtain arm 101 and the front curtain driven arm 102 and operate in conjunction with each other, and constitute a front curtain (front blade group) 150.

  Reference numeral 111 denotes a rear curtain arm that holds a rear blade group that constitutes the rear curtain of the shutter 5. The rear curtain arm engages with a foot portion 61 a of the rear curtain drive lever 61, and interlocks with the rear curtain drive lever 61 to center on the rotation center 111 a. Rotate. Reference numeral 112 denotes a rear curtain follower arm that holds the rear blade group and rotates around the rotation center 112 a in conjunction with the rear curtain arm 111. 113, 114, 115, and 116 are rear blades that are held by the rear curtain arm 111 and the rear curtain follower arm 112 and operate in conjunction with each other, and constitute a rear curtain (rear blade group) 160.

  FIG. 4 is a block diagram showing an electrical configuration built in the digital single-lens reflex camera having the configuration of FIG.

  Reference numeral 20 denotes a microcomputer (central processing unit, hereinafter referred to as “MPU”) that controls the camera unit and the entire camera. Reference numeral 21 denotes a memory controller that performs various types of control of image data, and 22 denotes an EEPROM that stores settings and adjustment data for performing various types of control.

  A lens control circuit 23 in the photographing lens 3 is connected to the MPU 20 via the mount 2 and performs focus adjustment (focus drive) and aperture drive of the focus lens based on each information described later.

  A focus detection circuit 24 performs accumulation control and readout control of the area sensor of the AF sensor 8 and outputs pixel information of each ranging point to the MPU 20. The MPU 20 performs focus detection on the pixel information of each distance measuring point by a known phase difference detection method, and sends the detected focus detection information to the lens control circuit 23 described above to perform focus adjustment of the focus lens. A series of operations from focus detection to focus adjustment is referred to as an autofocus (AF) operation.

  A photometric circuit 25 outputs a luminance signal from each area of the AE sensor 13 to the MPU 20. The MPU 20 performs A / D conversion of the luminance signal to obtain photometric information of the subject, and uses this photometric information to calculate and set an exposure suitable for photographing the subject. A series of operations from obtaining this photometric information to setting the photographic exposure is called an AE operation.

  A motor driving circuit 26 controls a motor (not shown) that drives the main mirror 4 and a motor (not shown) that charges the shutter 5.

  Reference numeral 27 denotes a shutter drive circuit that controls power supply to the front curtain coil 58 that holds the front curtain 150 of the shutter 5 in a charged state and the rear curtain coil 66 that holds the rear curtain 160 in a charged state.

  A DC / DC converter 28 converts the voltage of the power source 29 into a voltage necessary for each circuit.

  30 is a MODE button. When an electronic dial 32 (to be described later) is operated while being operated, the shooting mode is changed according to the count, and when the operation of the electronic dial 32 is stopped, the shooting mode when stopped is determined. A release button 31 is turned on by a first stroke (half-press) operation, is turned on by a switch SW1 for starting photometry (AE) and AF operations, and is turned on by a second stroke (full press), and a still image to be recorded is recorded. A signal of the switch SW2 for starting photographing is output to the MPU 20. Reference numeral 32 denotes an electronic dial. An ON signal corresponding to a dial rotation click is output to an up / down counter (not shown) in the MPU 20 and the number thereof is counted. Various numerical values and data are selected according to this count. Reference numeral 33 denotes a power button which is turned on / off when operated.

  Reference numeral 40 denotes a CDS (correlated double sampling) / AGC (automatic gain adjustment) circuit that samples and holds an image signal output from the image sensor 6 and performs automatic gain adjustment, and 41 converts an analog output of the CDS / AGC circuit 40 into a digital signal. This is an A / D converter. Reference numeral 42 denotes a TG (timing generation) circuit, which supplies a drive signal to the image sensor 6, a sample hold signal to the CDS / AGC circuit 40, and a sample clock signal to the A / D converter 41. That is, the TG circuit 42 constitutes a scanning control unit. Note that the memory controller 21 can detect the focus of the subject image by the contrast detection method. In that case, focus detection can be performed based on an image signal output from the image sensor 6 received through the CDS / AGC circuit 40 and the A / D converter 41.

  43 is an SDRAM for temporarily recording an image digitally converted by the A / D converter 41, 44 is a Y / C (luminance signal / color difference signal) separation, white balance correction, γ for the image signal. An image processing circuit that performs correction and the like. An image compression / decompression circuit 45 compresses the image signal in accordance with a format such as JPEG or decompresses the compressed image data. The memory controller 21 can process the image signal output from the image sensor 6 by the image processing circuit 44 to obtain photometric information of the subject. In this case, the MPU 20 calculates and sets an exposure value suitable for photographing the subject, that is, an exposure value that falls within a preset luminance range, using this photometric information.

  A D / A converter 46 converts an image signal into an analog signal in order to display an image recorded on the SDRAM 43 or a medium 48 described later on the liquid crystal monitor 14.

  Reference numeral 47 denotes an I / F (interface) with the medium 48 for recording and storing image signals.

  Next, the basic operation of the digital single lens reflex camera having the above-described configuration will be described with reference to the flowchart of FIG.

  In step S101, the power button 33 is operated to turn on the camera. At this time, it is assumed that the charge lever 52 charges a drive spring (not shown) and moves the front curtain and rear curtain of the shutter 5 to the charging position.

  In step S102, various buttons are operated to perform various camera settings. Here, the MODE button 30 is operated to set the shooting mode to shutter speed priority AE, and then the electronic dial 32 is operated to set the shutter speed.

  In step S103, it is determined whether or not the live view is used for shooting. If the live view display is ON, a live view shooting routine (step S100) is performed. Details of the live view shooting routine will be described later with reference to FIGS. 6A and 6B. For example, in the configuration shown in FIG. 4, the electronic dial 32 can be used to switch the live view shooting ON / OFF. On the other hand, if not ON, the process proceeds to step S104 of the normal photographing routine.

  In step S104, the release button 31 is pressed halfway to turn on the switch SW1. Accordingly, a predetermined AF operation is performed in step S105, and a predetermined AE operation is performed in step S106.

  In step S107, it is determined whether or not the release button 31 is fully pressed and the switch SW2 is turned on. If not turned on, the process returns to step S105, and the AF operation in step S105 and the AE operation in step S106 are repeated to wait for the switch SW2 to be turned on.

  If the switch SW2 is ON, the process proceeds to step S108, and the lens control circuit 23 drives the diaphragm of the photographing lens 3 in accordance with the diaphragm calculated in step S106.

  In step S109, the shutter drive circuit 27 controls the energization of the front curtain coil 58 and the rear curtain coil 66. When energized, the front curtain yoke 57 and the front curtain armature 54, and the rear curtain yoke 65 and the rear curtain armature 62 are adsorbed to each other.

  In step S110, the motor drive circuit 26 controls the energization of the motor, drives the charge lever 52, and releases the shutter 5 from the charged state. The shutter 5 at this time is in the state shown in FIGS. In step S111, the motor is controlled by the motor drive circuit 26, and the main mirror 4 and the sub mirror 7 are retracted from the photographing optical path (so-called mirror up).

  In step S112, in order to run the front curtain 150 (mechanical front curtain) of the shutter 5, the energization of the front curtain coil 58 is turned off by the shutter drive circuit 27. As a result, the electromagnetic force generated in the front curtain yoke 57 disappears, the electromagnetic attraction between the front curtain yoke 57 and the front curtain armature 54 is eliminated, and the front curtain drive lever 53 is moved by a front curtain drive spring (not shown). Turn right by the biasing force. Then, the front curtain 150 linked with the front curtain drive lever 53 travels from the position covering the aperture 51a to the retracted position. The camera at this time is in the state shown in FIG. 7, and the shutter 5 is in the state shown in FIGS.

  Thus, imaging (exposure) is started by the front curtain 150 traveling (step S113).

  In step S114, the elapsed time (exposure time of the image sensor 6) from the start of traveling of the front curtain 150 (the coil 58 is turned off) is measured, and it is determined whether or not the time corresponding to the calculated shutter speed has elapsed. I do. If it has not elapsed, time measurement is continued, and if it has elapsed, the process proceeds to step S115.

  In step S115, in order to drive the rear curtain 160 (mechanical rear curtain) of the shutter 5, the energization of the rear curtain coil 66 is turned off by the shutter drive circuit 27. As a result, the electromagnetic force generated in the rear curtain yoke 65 disappears, the electromagnetic attraction between the rear curtain yoke 65 and the rear curtain armature 62 disappears, and the rear curtain drive lever 61 is driven by a not-shown rear curtain drive spring. Turn right by the biasing force. Then, the rear curtain 160 that is interlocked with the rear curtain drive lever 61 travels from the position retracted from the aperture 51a to the cover position.

  In step S116, the charge (image signal) obtained by photoelectrically converting the optical image received by the image sensor 6 by the memory controller 21 is read via the CDS / AGC circuit 40 and the A / D converter 41, and is read into the SDRAM 43. Save temporarily. Then, after various image processing is performed by the image processing circuit 44 and the image compression / decompression circuit 45, the processed image signal is recorded on the medium 48.

  In step S117, the motor is controlled by the motor drive circuit 26, and the main mirror 4 and the sub mirror 7 retracted from the photographing optical path are driven to an observation position that reflects and guides the photographing light beam to the viewfinder (so-called mirror down). Further, the motor drive circuit 26 controls energization of the motor to drive the charge lever 52 to charge the shutter 5.

  In step S118, it is determined whether or not the power of the camera is turned off by operating the power button 33. If not, the process returns to step S102 to prepare for the next shooting, and if it is turned off, a series of shooting operations are performed. finish.

  Next, an operation routine when live view shooting in step S100 is selected will be described with reference to the flowcharts of FIGS. 6A and 6B.

  First, in step S120, a timer for measuring the continuous execution time of the live view display is started. In the next step S121, energization control for the front curtain coil 58 and the rear curtain coil 66 is performed by the shutter drive circuit 27. Do. When the front curtain coil 58 and the rear curtain coil 66 are energized, the front curtain yoke 57 and the front curtain armature 54, and the rear curtain yoke 65 and the rear curtain armature 62 are attracted to each other.

  In step S122, the motor drive circuit 26 controls energization of the motor, drives the charge lever 52, and releases the shutter 5 from the charged state. The shutter 5 at this time is in the state shown in FIGS. In step S123, the motor is controlled by the motor drive circuit 26, and the main mirror 4 and the sub mirror 7 are mirrored up.

  In step S124, in order to run the front curtain 150 (mechanical front curtain) of the shutter 5, the energization of the front curtain coil 58 is turned off by the shutter drive circuit 27. As a result, the electromagnetic force generated in the front curtain yoke 57 disappears, the electromagnetic attraction between the front curtain yoke 57 and the front curtain armature 54 is eliminated, and the front curtain drive lever 53 is moved by a front curtain drive spring (not shown). Turn right by the biasing force. Then, the front curtain 150 linked with the front curtain drive lever 53 travels from the position covering the aperture 51a to the retracted position. The camera at this time is in the state shown in FIG. 7, and the shutter 5 is in the state shown in FIGS.

  In step S <b> 125, imaging is started, and an image received by the image sensor 6 is periodically read by the memory controller 21 and temporarily recorded in the SDRAM 43. In step S127, the live view is started by continuously displaying the images temporarily recorded in the SDRAM 43 by the memory controller 21 on the liquid crystal monitor 14.

  When the live view is started, since the AF sensor 8 cannot be used because the mirror is raised, a contrast detection AF (so-called TV-AF) operation using the image sensor 6 is performed (step S127). Similarly, since the AE sensor 13 cannot be used due to mirror up, an AE (so-called TV-AE) operation using the image sensor 6 is performed (step S128).

  In step S129, it is confirmed whether the live view display remains ON. If ON, the process proceeds to step S130, and if OFF, the process returns to step S104 in FIG.

  In step S130, it is determined whether or not the count measured by the live view timer has reached the set live view continuation execution time T (first time). If it has reached, the process proceeds to step S131. If not reached, the process proceeds to step S132.

  Here, since the shutter is in a so-called valve state from Step S124 to Step S133 when the energization of the rear curtain coil 66 is started, the rear curtain coil 66 generates heat more and the temperature rises with time. If the live view display execution time is short, the temperature rise will be small, but if it is long, the temperature rise will become large, and the cutting characteristics of the rear curtain armature 62 will change. Depending on the shutter speed used at the time of shooting, uneven accuracy, exposure unevenness, etc. Will occur. Therefore, the live view timer is determined in step S130.

  If it is determined in step S130 that the continuous execution time of the live view display has exceeded the live view continuous execution time T, a display to the effect that the still image shooting sequence is changed is displayed on the liquid crystal monitor 14 in step S131. To do. This is to warn the photographer in advance because the photographer is surprised when the camera suddenly operates in a different sequence during still image shooting. If the live view continuation execution time T is not exceeded, the process proceeds to step S132 without displaying step S131.

  In step S132, it is determined whether or not the release button 31 is half-pressed during execution of the live view display (whether the switch SW1 is ON). If it is OFF, the process returns to step S127 to continue the live view display. If there is, the process proceeds to step S133.

  In step S133, it is determined whether or not the release button 31 is fully pressed and the switch SW2 is turned on. If the switch SW2 is turned on, the process proceeds to step S134 in FIG. 6B. If not, the process returns to step S132. The above determination is repeated.

  In step S134, it is determined again whether or not the count measured by the live view timer has reached the live view continuation execution time T (first time). If it has reached, the process proceeds to step S135. If not, the process proceeds to step S136. Even if it is determined that the live view continuation execution time T has not been reached in step S130, the live view continuation execution time T may be exceeded depending on the time lag until the switch SW2 is turned on in step S133. Judgment again.

In step S135, whether or not the shutter speed set by the photographer is equal to or greater than a predetermined value (longer than the preset time, ie, the shutter speed is slow) (shorter than the preset time, ie, the shutter speed). Is fast). The predetermined value used in step S135 corresponds to the second time. It is not less than the predetermined value, i.e., if the shutter speed is fast proceeds to step S 140, if more than a predetermined value, i.e., the process proceeds to step S 136 if the shutter speed is slow.

  Next, the elapsed time from the start of the live view and how the temperature changes will be described with reference to FIG.

  FIG. 10 shows the temperature change during live view execution and when live view is canceled. During live view execution, the temperature Ta of the rear curtain coil 66 is greatly increased as the live view duration (rear curtain energization time) increases.

  During live view execution, energization of the front curtain coil 58 is turned off, so that the temperature Ts of the front curtain coil 58 has a small rate of temperature rise compared to the temperature Ta of the rear curtain coil 66 and does not change much. . Therefore, the temperature difference ΔT (= Ta−Ts) of the rear curtain coil 66 and the front curtain coil 58 is greatly increased as the live view duration (rear curtain energization time) increases.

  On the other hand, after the live view is released, the temperature Ta of the temperature Ts of the front curtain coil 58 starts to rapidly decrease as time elapses from the live view release (elapsed time since the rear curtain energization is turned off). The temperature difference ΔT between the coil 66 and the leading curtain coil 58 is also lowered.

  In other words, by releasing the hold of the rear curtain from Live View shooting and charging the rear curtain again (the power is cut off for a short time from the release of the rear curtain hold to the recharge), ΔT is lowered. I can.

  As described above, if the duration of the live view display is short, the temperature rise of the trailing curtain coil 66 is small, but if the duration is long, the temperature rise becomes large and the cutting characteristic of the trailing curtain armature 62 changes. Depending on the shutter speed used at the time of shooting, unevenness in accuracy, exposure unevenness, etc. may occur, but this determination is performed because the influence on the unevenness in accuracy and unevenness of exposure decreases with decreasing shutter speed. In addition, since the reference value used for the determination is not uniformly determined by the shutter to be used, the product grade, or the like, it is desirable to set it for each product based on the actual measurement value.

  As described above, if the duration of the live view is short, and if the shutter speed is slow even if the duration is long, reset scanning of the image sensor 6 is performed in step S136. Here, the pixels of the image sensor 6 are reset sequentially for each pixel or line (the accumulated charge amount of the pixels is made zero), but charge accumulation in the image sensor 6 is started immediately after this reset scanning. Therefore, this reset scanning is called “electronic front curtain”. In step S136, the passage of time from the start of the electronic front curtain is measured, and it is determined whether or not the time (exposure time) corresponding to the set shutter speed has passed (step S137). If it has not elapsed, time measurement is continued, and if it has elapsed, the process proceeds to step S138.

  In step S138, the shutter drive circuit 27 turns off the energization of the rear curtain coil 66 in order to run the rear curtain 160 (mechanical rear curtain) of the shutter 5. As a result, the electromagnetic force generated in the rear curtain yoke 65 disappears, the electromagnetic attraction between the rear curtain yoke 65 and the rear curtain armature 62 disappears, and the rear curtain drive lever 61 is driven by a not-shown rear curtain drive spring. Turn right by the biasing force. Then, the rear curtain 160 that is interlocked with the rear curtain drive lever 61 travels from the position retracted from the aperture 51a to the cover position.

  In step S139, the electric charge (image signal) obtained by photoelectrically converting the optical image received by the image sensor 6 by the memory controller 21 is read via the CDS / AGC circuit 40 and the A / D converter 41 and stored in the SDRAM 43. Save temporarily. Then, after various image processing is performed by the image processing circuit 44 and the image compression / decompression circuit 45, the processed image signal is recorded on the medium 48.

  With the operations from step S137 to step S139, the still image shooting sequence (second shooting process) using both the electronic front curtain and the mechanical rear curtain is completed.

  On the other hand, if it is determined in step S135 that the shutter speed set by the photographer is not equal to or greater than the predetermined value (second time), a warning is displayed in step S140. Here, since the duration of the live view display exceeds the live view duration execution time T, if still image shooting is performed at the set shutter speed, the above-described still image shooting using both the electronic front curtain and the mechanical rear curtain is performed. Warning that the sequence will be different from the sequence.

  In step S141, the shutter drive circuit 27 turns off the energization of the rear curtain coil 66 in order to run the rear curtain 160 (mechanical rear curtain) of the shutter 5. As a result, the electromagnetic force generated in the rear curtain yoke 65 disappears, the electromagnetic attraction between the rear curtain yoke 65 and the rear curtain armature 62 disappears, and the rear curtain drive lever 61 is driven by a not-shown rear curtain drive spring. Turn right by the biasing force. Then, the rear curtain 160 that is interlocked with the rear curtain drive lever 61 travels from the position retracted from the aperture 51a to the cover position.

  In step S142, the motor is controlled by the motor driving circuit 26, and the main mirror 4 and the sub mirror 7 retracted from the photographing optical path are driven to an observation position that reflects and guides the photographing light flux to the viewfinder (so-called mirror down). Further, the motor drive circuit 26 controls energization of the motor, drives the charge lever 52 to charge the shutter 5, and proceeds to step S143.

  Since the process of step S143-step S151 is the same as the process demonstrated by step S108-S117 of FIG. 5, description is abbreviate | omitted.

  With the operations from step S141 to step S151, the still image shooting sequence (first shooting process) using both the mechanical front curtain and the mechanical rear curtain is completed.

  In step S152, the motor is controlled by the motor drive circuit 26, and the main mirror 4 and the sub mirror 7 retracted from the imaging optical path are driven to an observation position that reflects and guides the imaging light beam to the viewfinder (so-called mirror down). Further, the motor drive circuit 26 controls energization of the motor to drive the charge lever 52 to charge the shutter 5. Thereafter, the process returns to step S121 in FIG. 6A to continue the live view display.

  As described above, according to the present embodiment, when the live view display duration time is long and the shutter speed is fast, still image shooting is performed using the mechanical front curtain and the mechanical rear curtain. In addition, still image shooting is performed using an electronic front curtain and a mechanical rear curtain. If the live view display continues for a long time, the shutter accuracy due to the change in the cut-off characteristic cannot be guaranteed. Therefore, the change in the cut-off characteristic is suppressed by once releasing the suction holding state of the trailing curtain. As a result, it is possible to prevent deterioration of shutter accuracy and to prevent uneven exposure.

  In the above description, the shooting mode is set to the shutter speed priority AE in step S102, but aperture priority AE may be used. In that case, the determination is made based on the set aperture and the shutter speed obtained from the photometric information. The same applies to other shooting modes.

  Further, in the above embodiment, a warning is issued in step S140 that the still image shooting sequence is different from the still image shooting sequence using both the electronic front curtain and the mechanical rear curtain, that is, the mechanical front curtain and the mechanical rear curtain are used. Explained the case. However, the present invention is not limited to this, and a warning is issued before step S136 that it is a still image shooting sequence when live view display is not performed, that is, the electronic front curtain and the mechanical rear curtain are used. It doesn't matter if you do. In each case, the user may be notified of each still image shooting sequence. Moreover, it is good also as a specification which does not perform warning display.

  Of course, various modifications and applications can be made without departing from the gist of the invention as long as the functions of the above-described embodiments can be achieved.

It is the schematic which shows the cross section of the digital single-lens reflex camera concerning embodiment of this invention. It is a schematic front view of the shutter concerning embodiment of this invention. It is a schematic rear view of the shutter concerning an embodiment of the invention. It is a block diagram which shows the electrical constitution of the digital single-lens reflex camera concerning embodiment of this invention. It is a flowchart which shows the basic operation | movement of the digital single-lens reflex camera concerning embodiment of this invention. It is a flowchart which shows the operation | movement in the live view display of the digital single-lens reflex camera concerning embodiment of this invention. It is a flowchart which shows the operation | movement in the live view display of the digital single-lens reflex camera concerning embodiment of this invention. It is the schematic which shows the cross section of the digital single-lens reflex camera in the live view display concerning embodiment of this invention. It is a schematic front view of the shutter in the live view display concerning embodiment of this invention. It is a schematic rear view of the shutter during live view display according to the embodiment of the present invention. It is a graph which shows the change of the front curtain temperature Ts, the rear curtain temperature Ta, and the temperature difference (DELTA) T with the elapsed time from the live view start of the focal plane shutter in embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Camera body 2 Mount 3 Shooting lens 4 Main mirror 5 Shutter 6 Image sensor 7 Sub mirror 8 AF sensor 9 Focus plate 10 Pentaprism 11, 12 Eyepiece 13 AE sensor 14 Liquid crystal monitor 53 Front curtain drive lever 54 Front curtain armature 57 Front curtain Yoke 58 Front-curtain coil 61 Rear-curtain drive lever 62 Rear-curtain armature 65 Rear-curtain yoke 66 Rear-curtain coil 67 Rear-curtain bobbin 150 Front-curtain 160 Rear-curtain

Claims (5)

An image sensor for photographing a subject;
  A mechanical shutter that includes a traveling curtain that travels in a direction that blocks incident light on the image sensor, and a curtain holding mechanism that retains the traveling curtain at an initial position before traveling by electromagnetic force;
  Time measuring means for measuring the energization time to the curtain holding mechanism;
  When the energization time measured by the time measuring unit when a still image shooting is instructed is a predetermined time or longer, the running curtain is made to travel before starting exposure for still image shooting, and the running curtain is turned on after running. Control means for starting the exposure after being held at the initial position by the curtain holding mechanism;
  An imaging device comprising:   The control means does not run the running curtain before starting the exposure when the energization time measured by the time measuring means is less than a predetermined time when a still image shooting is instructed. The imaging device according to claim 1.   The control means, when still image shooting is instructed, when the energization time measured by the time measuring means is a predetermined time or more and the shutter speed at the time of still image shooting is shorter than a predetermined value, 3. The exposure according to claim 1, wherein the running curtain is run before the exposure is started, and the exposure is started after the running curtain is held at the initial position by the curtain holding mechanism after running. Imaging device.   A scanning control means for controlling reset scanning of the image sensor;
  The mechanical shutter has a second traveling curtain that travels in a direction in which the incident light is incident from a state in which incident light to the image sensor is blocked, and the second traveling curtain is held at an initial position before traveling by electromagnetic force. And a second curtain holding mechanism that
  When the energizing time measured by the time measuring means is equal to or longer than a predetermined time when the still image shooting is instructed in a state where the second running curtain is already running, the control means The exposure is started by running the running curtain after being held at the initial position by the second curtain holding mechanism, and when the energization time is less than a predetermined time, the exposure is performed by performing the reset scanning. The imaging apparatus according to claim 1, wherein the imaging apparatus is started.   A mechanical shutter including an image sensor for photographing a subject, a traveling curtain that travels in a direction that blocks incident light on the image sensor, and a curtain holding mechanism that retains the traveling curtain at an initial position before traveling by electromagnetic force And a method of controlling an imaging apparatus comprising:
  A time measuring step for measuring a current-carrying time to the curtain holding mechanism;
  When the control unit is instructed to shoot still images and the energization time measured in the time measurement step is equal to or longer than a predetermined time, the controller drives the running curtain before starting the exposure of the still image, A control step of starting the exposure after holding the traveling curtain at the initial position by the curtain holding mechanism;
  A method for controlling an imaging apparatus, comprising:

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