JP5963590B2 - Imaging device - Google Patents

Description

  The present invention relates to an imaging apparatus, and more particularly to an imaging apparatus having an imaging element and a focal plane shutter.

  In an imaging apparatus having an imaging element and a focal plane shutter, exposure is controlled by the accumulation time of light received by the imaging element.

  For example, in Patent Document 1, charge accumulation is started by an electronic shutter while the focal plane shutter is open, the focal plane shutter is closed, and charge is read. Then, the focal plane shutter is opened again after the charge reading of the image sensor is completed.

Japanese Patent No. 4196437

  However, in Patent Document 1, since the focal plane shutter is opened after charge reading is completely completed, there is a problem that it takes a long time to start the imaging operation again after imaging.

  In view of such a problem, an object of the present invention is to provide an imaging apparatus capable of shortening the time until the imaging operation is started again after imaging.

An imaging apparatus according to an aspect of the present invention is an image sensor that photoelectrically converts a subject image to generate an image signal, and a light shield that is disposed in front of the image sensor and shields the image sensor by moving a blade group. And a focal plane shutter that switches to an exposure state that exposes the image sensor , wherein the image sensor reads and scans the image signal, and the focal plane shutter switches from the light shielding state to the exposure state. The moving direction of the blade group in the same direction is set to the same direction, and before the readout scanning of the image signal is completed, the focal plane shutter moves the image sensor from the light shielding state to the exposure state. The focal plane shutter starts to move, and the area where the image signal is not read out is the exposure. And wherein the moving the blade set so as not on purpose.

  ADVANTAGE OF THE INVENTION According to this invention, the imaging device which enabled shortening the time until it starts an imaging operation again after imaging | photography can be provided.

1 is an external perspective view of an imaging apparatus according to an embodiment of the present invention. It is a block diagram of an imaging device. It is a whole block diagram of an image sensor. It is a circuit diagram in one pixel of an image sensor. It is a circuit diagram of a column common readout circuit. It is a timing chart which shows read-out operation of each line of an image sensor. It is a timing chart which shows the operation | movement per line in the reset scanning of an image pick-up element, and a moving image read-out scanning. It is a disassembled perspective view of a focal plane shutter. It is an operation | movement figure of the blade group of a focal plane shutter. It is a front view of a cam gear. It is a figure showing the operation timing of each component of a focal plane shutter and an image pick-up element. It is a figure showing the positional relationship of the component at the time of reading the image signal of an image pick-up element. It is a figure showing the reading position of the image signal of an image sensor, and the position of a blade group. It is a figure which shows the relationship between a power supply voltage and the opening speed of a blade group. It is a figure showing the reading position of the image signal of an image sensor, and the position of a blade group.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is an external perspective view of an imaging apparatus which is an example of an embodiment of the present invention.

  On the upper surface of the imaging apparatus 100, an accessory shoe 140 for attaching a photographing accessory such as a power button 110, a release button 130, and a flash device is provided. The lens mount 150 is an attachment portion for a photographing lens (not shown).

  Since the imaging apparatus 100 is a mirrorless type imaging apparatus having no reflex mirror, the shutter curtain is opened in a shooting standby state for live view display. Therefore, as shown in FIG. 1, the image pickup surface of the image pickup device 3 is exposed in a state where the photographing lens is removed.

  FIG. 2 is a block diagram of the imaging apparatus 100.

  The focal plane shutter 2 is provided between the imaging lens 1 and the imaging device 3 on the imaging optical path, and adjusts the time for exposing the imaging device 3 in conjunction with the electronic front curtain operation of the imaging device 3.

  The image sensor 3 uses a CMOS image sensor or the like, and photoelectrically converts a subject image formed by the imaging lens 1 that forms light from the subject. An analog image signal generated and output by the image sensor 3 is converted into a digital signal by an AFE (Analog Front End) 4. The digital image signal output from the AFE 4 is subjected to various image processing, compression / decompression processing, and the like by a DSP (Digital Signal Processor) 5.

  The recording medium 6 records image data processed by the DSP 5. The display unit 7 uses a liquid crystal display (LCD) or the like, and displays captured images and various menu screens.

  The image sensor driving circuit 8 controls driving of the image sensor 3. The RAM 10 is connected to the DSP 5 and temporarily stores image data and the like. The shutter drive circuit 11 drives the focal plane shutter 2.

  The CPU 9 controls the AFE 4, the DSP 5, the image sensor driving circuit 8, and the shutter driving circuit 11.

  Reference numeral 91 denotes voltage detection means for detecting the power supply voltage of the imaging apparatus 100, reference numeral 92 denotes temperature detection means for detecting the temperature inside the imaging apparatus 100, and reference numeral 93 denotes state detection means provided in the focal plane shutter 2. A lens control unit 94 outputs lens information such as a focal length, an aperture diameter, an exit pupil diameter, an exit pupil-to-image sensor distance, and the like of the imaging lens 1 to the CPU 9, and controls the aperture, the lens, and the like according to control by the CPU 9. To drive. The detection result of each detection means is input to the CPU 9.

  Next, the imaging operation will be described. FIG. 3 is an overall configuration diagram of the image sensor 3, and FIG. 4 is a circuit diagram in one pixel of the image sensor 3.

  In the pixel area PA, the pixel units 20 are arranged on a matrix like p11 to pkn.

  Here, a circuit diagram in one pixel of the pixel portion 20 will be described with reference to FIG.

  A photodiode (hereinafter referred to as PD) 41 photoelectrically converts an incident optical signal and accumulates electric charges according to the exposure amount.

  The charges accumulated in the PD 41 are transferred to the FD (floating diffusion) unit 43 by setting the signal tx of the transfer gate 42 to the high level.

  The FD unit 43 is connected to the gate of a floating diffusion amplifier 44 (hereinafter referred to as an FD amplifier), and the amount of charge transferred from the PD 41 by the FD amplifier 44 is converted into a voltage amount.

  When the signal res of the FD reset switch 45 is set to High level, the FD unit 43 is reset. When resetting the charge of the PD 41, the signal tx and the signal res are simultaneously set to the high level, so that both the transfer gate 42 and the FD reset switch 45 are turned on, and the PD 41 is reset via the FD unit 43. become.

  By setting the signal sel of the pixel selection switch 46 to a high level, the pixel signal converted into a voltage by the FD amplifier 44 is output to the output vout of the pixel unit 20.

  Returning to FIG. 3, the vertical scanning circuit 21 supplies drive signals such as res_1, tx_1, sel_1, and the like to each pixel. These drive signals are connected to res, tx, and sel of each pixel, respectively. The output vout of each pixel is connected to the column common readout circuit 23 via the vertical output line 22 for each column.

  Here, a circuit diagram of the column common readout circuit 23 will be described with reference to FIG.

  The vertical output line 22 is provided for each column, and the output vout of the pixel unit 20 for one column is connected thereto. A current source 24 is connected to the vertical output line 22, and a source follower circuit is configured by the current source 24 and the FD amplifier 44 in each pixel of the pixel unit 20.

  The pixel signal S read from the pixel unit 20 is stored in the S signal holding capacitor 53 via the S signal transfer switch 51 by setting the signal ts to a high level.

  The noise signal N read from the pixel unit 20 is stored in the N signal holding capacitor 54 via the N signal transfer switch 52 by setting the signal tn to a high level.

  The S signal holding capacitor 53 and the N signal holding capacitor 54 are connected to the outputs vs and vn of the column common readout circuit 23, respectively.

  Returning to FIG. 3, horizontal transfer switches 25 and 26 are connected to the outputs vs and vn of the column common readout circuit 23, respectively.

  The horizontal transfer switches 25 and 26 are controlled by an output signal hsr * (* is a column number) of the horizontal scanning circuit 27. When the signal hsr * becomes a high level, the signals of the S signal holding capacitor 53 and the N signal holding capacitor 54 Are transferred to the horizontal output lines 28 and 29, respectively.

  The horizontal output lines 28 and 29 are connected to the input of the differential amplifier 30. The differential amplifier 30 obtains a difference between the S signal and the N signal and simultaneously applies a predetermined gain, and outputs a final image signal to the output terminal 31. Output to.

  The horizontal output line reset switches 32 and 33 are turned ON when the signal chres becomes High, and the horizontal output lines 28 and 29 are reset to the reset voltage Vchres.

  Next, still image readout scanning of the image sensor 3 will be described with reference to FIG. FIG. 6 is a timing chart showing operations per row in the reset scanning and still image reading scanning of the image sensor 3. Here, description will be made assuming that the data in the i-th row is read.

  First, the signal sel_i is set to the High level, and the pixel selection switch 46 of the pixel in the i-th row is turned on.

  Thereafter, the signal res_i is set to the Low level, the FD reset switch 45 is turned OFF, and the reset of the FD unit 43 is released.

  Next, the signal tn is set to the high level, and the N signal is stored in the N signal holding capacitor 54 via the N signal transfer switch 52.

  Subsequently, the signal tn is set to Low, the N signal transfer switch 52 is turned OFF, the signal ts is set to High level, the S signal transfer switch 51 is turned ON, and the transfer gate 42 is turned ON by setting the signal tx_i to High level. .

  By this operation, the signal accumulated in the PD 41 in the selected i-th row is output to the vertical output line 22 via the FD amplifier 44 and the pixel selection switch 46, and further, the S signal is transferred via the S signal transfer switch 51. It is stored in the signal holding capacitor 53.

  Next, after the signals tx_i and ts are set to Low level and the transfer gate 42 and the S signal transfer switch 51 are closed, the signal res_i is set to High level and the FD reset switch 45 is turned on to reset the FD unit 43.

  By the operation so far, the operation of storing the N signal and the S signal in the i-th row in the S signal holding capacitor 53 and the N signal holding capacitor 54 is finished.

  Subsequently, an operation of outputting the S signal and the N signal stored in the S signal holding capacitor 53 and the N signal holding capacitor 54 from the image sensor 3 is performed.

  First, when the output hsr1 of the horizontal scanning circuit 27 becomes a high level, the horizontal transfer switches 25 and 26 are turned ON, and the signals of the S signal holding capacitor 53 and the N signal holding capacitor 54 are differentially compared with the horizontal output lines 28 and 29. The signal is output to the output terminal 31 through the amplifier 30.

  The horizontal scanning circuit 27 outputs all data in the i-th row by sequentially setting the selection signals hsr1, hsr2,..., Hsrk of each column to High.

  While the signals of each column are read by the signals hsr1 to hsrk, the horizontal output line reset switches 32 and 33 are turned on by setting the signal chres to the high level, and the horizontal output lines 28 and 29 are once set to the reset voltage. Reset to Vchres level.

  This completes the reading operation for one row. By repeating this operation for each row, signals of all rows of the image sensor 3 are read out.

  Next, a live view imaging operation for moving image shooting or an electronic viewfinder function will be described.

  First, reset scanning of the image sensor 3 is started, and accumulation of each row is sequentially started.

  After a predetermined time has elapsed from the start of reset scanning, moving image readout scanning is started. The time from the start of reset scanning to the start of moving image readout scanning is the electronic shutter time. This reset scanning and moving image readout scanning are performed, for example, by thinning out rows every three rows due to frame rate restrictions. For this reason, the time required for reset scanning and moving image readout scanning is shorter than the time required for still image readout scanning, and each can be completed within one frame time such as 30 frames / second.

  FIG. 7 is a timing chart showing operations per row in reset scanning and moving image reading scanning of the image sensor 3. Here, the row in which reset scanning is performed will be described as the j-th row, and the row in which moving image reading scanning is performed will be described as the i-th row.

  First, in the reset scanning row, the signal res_j is held at a high level, and the signal sel_j is held at a low level. In this state, by setting the signal tx_j to the high level, the PD 41 in the j-th row is reset. Next, by setting the signal tx_j to the low level, the reset of the PD 41 is finished and the storage state is entered.

  In the moving image readout scanning row, the same operation as the still image readout scanning described in FIG.

  By repeating this operation for each row, reset scanning / moving image reading scanning is performed. In addition, after the reset scanning / moving image reading scanning of the first frame, the reset scanning / moving image reading scanning of the second and subsequent frames is similarly repeated.

Next, the focal plane shutter 2 disposed in front of the image sensor 3 will be described.

  FIG. 8 is an exploded perspective view of the focal plane shutter 2. FIG. 8A is an exploded perspective view of the focal plane shutter 2 as viewed from the side (hereinafter referred to as the front) where the imaging lens 1 is attached, and FIG. 8B is the side where the imaging element 3 is attached (hereinafter referred to as the back). It is the disassembled perspective view seen from.

  The shutter base plate 201 is fixed inside a camera body (not shown), and each component constituting the driving mechanism of the blade group 230 is attached.

  The blade drive member 202 and the cam gear (charge member) 203 are rotatably supported on the shafts 201a and 201b of the shutter base plate 201, respectively.

  A driving spring (not shown) is disposed on the outer periphery of the shaft 201a of the shutter base plate 201 on which the blade driving member 202 is rotatably supported. The drive spring urges the blade drive member 202 in the counterclockwise direction (the traveling direction of the blade group 230) in FIG.

  The auxiliary base plate 205 is engaged with and attached to the tips of the shafts 201a and 201b of the shutter base plate 201.

  The photo sensor 207 is attached to the auxiliary base plate 205. The light shielding portion 202c of the blade driving member 202 shields the photosensor 207, thereby detecting the rotational position of the blade driving member 202. As the blade driving member 202 rotates, the blade group 230 expands and overlaps, so that the photosensor 207 detects the rotational position of the blade driving member 202, thereby detecting the position of the blade group 230 at the opening 201d. It becomes possible. That is, the photosensor 207 functions as part of the state detection unit 93.

  The yoke 210 and the coil 211 are respectively fixed to the auxiliary ground plate 205 with screws (not shown).

  The motor (drive source) 220 has an output shaft in the same direction as the photographing optical axis disposed on the mounting surface 201 c of the shutter base plate 201. The motor 220 can control the driving speed by changing the driving voltage. In this embodiment, speed control of the charging operation is realized by PWM control of the voltage applied to the motor 220 by the shutter drive circuit 11.

  When the cam gear 203 is rotated by the driving force transmitted from the motor 220 via the reduction gear train 221, the blade driving member 202 is rotated following the cam gear 203. At this time, a charge operation for charging the drive spring and a charge release operation for releasing the drive spring can be performed.

  The cover plate 206 is fixed to the back side of the shutter base plate 201. An opening 206 a is provided at a position substantially coincident with the opening 201 d of the shutter base plate 201 at the center of the cover plate 206. A blade chamber in which the blade group 230 is disposed is formed between the shutter base plate 201 and the cover plate 206.

  The blade group 230 includes a first blade 231, a second blade 232, a third blade 233, a main arm 234, and a sub arm 235.

  Each blade is made of polyethylene terephthalate containing a black paint, and is rotatably supported by the main arm 234 and the sub arm 235 to form a parallel link.

  The main arm 234 and the sub arm 235 are rotatably supported by the shaft 201e and the shaft 201f of the shutter base plate, respectively.

  The main arm 234 is provided with a hole 234a for engaging with the driving pin 202a of the blade driving member 202. The drive pin 202a passes through the groove 201g formed in the shutter base plate 201 and engages with the hole 234a.

  A blade backlash spring 236 is hung on the sub arm 235 in the clockwise direction, that is, in the traveling direction of the blade group 230 in FIG.

  Next, the configuration of the focal plane shutter 2 will be described in detail with reference to FIG. FIG. 9 is an operation diagram of the blade group 230 when the focal plane shutter 2 is viewed from the front. Note that the auxiliary ground plate 205 is omitted for easy viewing of the drawing.

  FIG. 9A shows an overcharged state of the blade driving member 202, that is, a state where the imaging device 100 is stopped. FIG. 9B shows a standby state before traveling of the blade group 230, and FIG. 9C shows a traveling completion state of the blade group 230. FIG. 9D shows a state in which the blade driving member 202 is ready for charging.

  When the driving pin 202a moves along the groove 201g by the rotation of the blade driving member 202, the main arm 234 rotates to expand and superimpose the blade group 230. By the operation of the blade group 230, the light beam passing through the focal plane shutter 2 is limited by opening and closing the opening 201d. Here, the rotation range of the blade driving member 202 is limited by the groove 201g.

  The blade driving member 202 is provided with an armature support portion 202b. A through hole portion (not shown) formed in the armature support portion 202b has a flange portion larger than the inner diameter of the through hole portion. On the other hand, the armature shaft 213 attached integrally is engaged. The armature shaft 213 extends in a direction substantially orthogonal to the suction surface of the armature 212.

  A compression spring (not shown) is disposed between the armature 212 and the armature support portion 202b and on the outer periphery of the armature shaft 213, and the armature 212 and the armature support portion 202b are separated from each other (vertical direction in FIG. 9). Is energized.

  When a voltage is applied to the coil 211, a magnetic force can be generated in the yoke 210, and the armature 212 can be attracted by this magnetic force.

  The cam top region 203 a and the cam inclined region 203 b formed on the cam gear 203 abut on the charge roller 204 provided on the blade driving member 202 according to the rotation of the cam gear 203 to rotate the blade driving member 202. .

  Here, the structure of the cam gear 203 will be described with reference to FIG. 10 which is a front view of the cam gear 203. A cam portion 203 a is formed on one surface of the cam gear 203. As shown in FIG. 10, the cam portion 203a is divided into four regions, a cam top region 203a-1, a cam inclined region 203a-2, a cam bottom region 203a-3, and a charge region 203a-4.

  Next, the imaging operation will be described with reference to FIG.

  FIG. 11 is a diagram illustrating the operation timing of each component of the focal plane shutter 2 and the image sensor 3. In addition, (1)-(11) in FIG. 11 respond | corresponds to each operation state.

In (1) of FIG. 11, the focal plane shutter 2 is in an overcharged state as shown in FIG. 9A, and the blade group 230 is superimposed, so that the subject luminous flux is passed (exposure state) .

  In the imaging apparatus 100, a live view imaging operation is performed, and a subject image incident on the imaging element 3 is displayed on an image display unit (not shown).

  When the release operation is started (FIG. 11B), the CPU 9 controls the shutter drive circuit 11, so that the shutter drive circuit 11 energizes the coil 211, generates a magnetic force in the yoke 210, and connects the yoke 210 and the armature 212. Set to adsorption state.

  After the yoke 210 and the armature 212 are brought into the suction state, the shutter drive circuit 11 energizes the motor 220 and rotates the cam gear 203 in the counterclockwise direction. The charge roller 204 moves from the state of tracing the cam top region 203a-1 of the cam gear 203 to the state of tracing the cam inclined region 203a-2. The charge lever 260 is gradually released from the overcharge state by tracing the cam inclined region 203a-2. Then, when the charge roller 204a enters a state where the cam bottom region is traced 203a-3, the state moves to the standby state before travel of the blade group 230 shown in FIG. 9B, and the shutter drive circuit 11 supplies power to the motor 220. Stop (FIG. 11 (3)).

  When the CPU 9 controls the image sensor driving circuit 8, the image sensor driving circuit 8 resets all the pixels of the image sensor 3 (FIG. 11 (4)). Specifically, the signals res_1 to res_n are set to the low level, the signals tx_1 to tx_n are set to the high level, and the PDs 41 of all the pixel units 20 in the first to nth rows are reset.

  Thereafter, the CPU 9 controls the image sensor driving circuit 8 so that the image sensor driving circuit 8 starts electronic front curtain scanning (FIG. 11 (5)). During the period from FIG. 11 (4) to FIG. 11 (5), the all-pixel reset state of the image sensor 3 is continued.

  Here, the electronic front curtain scanning refers to starting charge accumulation line by line with respect to the image sensor 3 in which all pixels are in a reset state. Specifically, the vertical scanning circuit 21 sequentially sets the signal tx_ * to the low level from the nth row to the first row. As a result, the reset of the PDs 41 in each row is sequentially released and enters the accumulation state.

Since the scanning pattern for starting charge accumulation line by line is a scanning pattern that matches the running characteristics of the blade group 230, the uniform accumulation time (exposure time) is obtained for any line of the image sensor 3. The CPU 9 controls the shutter drive circuit 11 so that after the electronic front curtain scan is started, the shutter drive circuit 11 turns off the coil 211 after a time interval corresponding to the set shutter time. Thus, the suction force worked between the yoke 251 and the armature 212 disappears (Fig. 11 (6)), the blade driving member 202 begins to rotate in the counterclockwise direction by the bias of the drive spring. As a result, the opening 201d is in a state where the subject light beam is blocked (light-shielded state) as shown in FIG. 9C (FIG. 11 (7)).

When the traveling of the blade group 230 of the focal plane shutter 2 is completed and the image sensor 3 is completely shielded from light, the CPU 9 controls the image sensor drive circuit 8 so that the image sensor drive circuit 8 starts a still image reading scan. To do. In the still image readout scanning, the charge accumulated in the PD 41 of each pixel is sequentially started from the first row by repeating the readout operation of the image signal for each row described in FIG. 6 along the readout scanning direction of the image signal . Read out. At this time, it is necessary to keep the light beam blocked in the area where the reading of the image signal is not completed.

  By the way, the cam gear 203 is provided with an idle running angle θ that becomes an idle running section of the motor 220 until the next charging operation is performed (until contact with the charge roller 204) as shown in FIG. 9C. . As for the idling angle θ, the overrun angle of the motor 220 varies greatly depending on the power supply voltage of the imaging apparatus 100 and the temperature of the photographing environment. Therefore, it is designed to have a sufficient angle so that the charge roller 204 does not come into contact with the cam gear 203 even when the overrun angle of the motor 220 becomes the largest.

  However, when the idling angle θ of the cam gear 203 is large, the charging time becomes long. Therefore, in this embodiment, the cam gear 203 is rotated by applying a voltage whose effective voltage has been changed by PWM control to the motor 220 within the readout period of the image signal (FIG. 11 (8)). As a result, the cam gear 203 rotates from the state where the idle running angle of the cam gear 203 is θ (FIG. 9C) to the state where the idle running angle of the cam gear 203 is θ ′ (FIG. 9D). At this time, in the state immediately after the travel of the blade group 230 is completed (FIG. 11 (7)), the blade group 230 vibrates, and thus the second predetermined time for converging the vibration of the blade group 230 has elapsed. Later, the driving of the idle section is started. That is, the time from FIG. 11 (7) to FIG. 11 (8) corresponds to a predetermined time (second predetermined time) for converging the vibration of the blade group 230.

  When a voltage whose effective voltage has been changed by PWM control is applied to the motor 220 and the idling angle of the cam gear 203 reaches θ ′ (FIG. 9D), the application of the voltage to the motor 220 is stopped. Then, the rotation of the cam gear 203 is stopped. In the present embodiment, the cam gear 203 is temporarily stopped before the charge operation start position.

  In the present embodiment, the cam gear 203 is temporarily stopped before the charge operation start position. Accordingly, when starting the charging operation, the charging operation is always started from the state where the cam gear 203 is stopped. If the charging operation is started without temporarily stopping the cam gear 203 before the charging operation start position, the rotational speed of the cam gear 203 when starting the charging operation is not constant, and the charging time is not constant.

  When the first predetermined time has elapsed from the start of reading of the image signal (FIG. 11 (7)), a voltage is applied to the motor 220 to start the charging operation.

  In this embodiment, the motor 220 is driven to reduce the idle running angle of the cam gear 203 between the start of image signal readout (FIG. 11 (7)) and the start of the charging operation (FIG. 11 (9)). Yes. Therefore, when starting the charging operation, the idle running section of the cam gear 203 is shortened, and the charging time can be shortened.

  In the present embodiment, the motor is operated from the state where the idle running angle of the cam gear 203 is θ (FIG. 9C) to the state where the idle angle of the cam gear 203 is θ ′ (FIG. 9D). A voltage whose effective voltage is changed by PWM control is applied to 220. Thereby, the stop position accuracy of the motor 220 is increased, and the idling angle θ ′ can be further reduced.

After the first predetermined time from the start of reading the image signal (FIG. 11 (9)), the CPU 9 controls the shutter drive circuit 11 so that the shutter drive circuit 11 energizes the motor 220 and turns the cam gear 203 counterclockwise. Rotate in the direction. As a result, the blade driving member 202 rotates clockwise against the urging force of the torsion coil spring to perform a charging operation. At this time, the blade group 230 moves along the moving direction in the same direction as the image signal readout scanning direction, and gradually overlaps to open the openings 201p in order from the line where the image signal readout is completed. . That is, in the present embodiment, the opening 201p starts to be opened before the reading of the image signals of all the pixels is completed. At this time, the charge start timing is set so that the light leaking from the portion where the blade group 230 is opened does not enter the pixels in the row where the still image readout scanning has not yet reached.

  After the readout of the image signals of all the pixels is completed (FIG. 11 (10)), the blade group 230 completes the superimposition and the opening 201d is in an open state. Then, the shutter drive circuit 11 stops energizing the motor 220 (FIG. 11 (11)). As a result, the blade driving member 202 is overcharged again.

  Since the charging time from FIGS. 11 (9) to 11 (11) is the charging operation from the idle running angle θ ′ in which the cam gear 203 is ready to be charged, the idle running angle θ−θ ′ is shortened. As a result, the time (2) to (11), which is the time possessed by one frame of the camera, is shortened, and the shooting speed of the camera can be increased.

  When the charging operation ends, the CPU 9 starts a live view imaging operation for the electronic viewfinder function.

  Next, the relationship between the blade group 230 and the image signal readout position of the image sensor 3 when the image sensor 3 reads the image signal will be described in detail.

  FIG. 12 is a diagram illustrating the positional relationship of the component parts when the image signal of the image sensor 3 is read. FIG. 13 is a diagram illustrating the reading position of the image signal of the image sensor 3 and the position of the tip of the blade group 230. The positional relationship of the components at time T4 in FIG. 13 is the state in FIG.

  In FIG. 12A, the lower side of the image signal readout line is an area where the opening operation of the blade group 230 is completed, and is an area where the image sensor 3 is exposed. Further, the black portion on the upper side of the image signal readout line is a region where the blade group 230 is not opened, and indicates a region where the image sensor 3 is shielded from light.

  A dashed line in FIG. 13A indicates the read position of the image signal of the image sensor 3 and the position of the tip of the blade group 230. For example, at time T4, the lower side of the alternate long and short dash line is a region where the opening operation of the blade group 230 is completed and a region where reading of the image signal of the image sensor 3 is completed, and the image sensor 3 is exposed. Further, the upper side of the alternate long and short dash line is a region where the blade group 230 is not opened and the image signal of the image sensor 3 is not read, and the image sensor 3 is shielded from light.

  However, the relationship shown in FIGS. 12A and 12A is established in the case of so-called parallel light in which a light beam is incident perpendicularly to the image sensor 3, and the light passing through the actual imaging lens 1 is imaged. Since the light is incident on the element 3 at an angle, it differs from the case of FIGS.

  Therefore, a case where incident light passes through the actual imaging lens 1 will be described with reference to FIGS. 12 (b) and 13 (b).

  In FIG. 12B, the light ray C that exits from the lower end of the exit pupil of the imaging lens 1 and passes through the lower end b of the blade group 230 reaches the position of the interval β (t) above the image signal readout line of the imaging device 3. Therefore, in the region of the interval β (t) from the image signal readout line, the image signal is affected because the exposure is performed in a state where the readout of the image signal is not performed.

The interval β (t) is D for the exit pupil diameter of the imaging lens 1, L for the distance between the exit pupil of the imaging lens 1 and the imaging device, x for the distance between the blade group 230 and the imaging device, and the optical axis and image of the imaging lens 1. If the distance from the signal readout position is h (t),
β (t) = x (D / 2−h (t)) / (L−x)
It is represented by

  This state will be described with reference to FIG. An alternate long and short dash line is an image signal readout line, and an alternate long and two short dashes line connects the image signal readout line with a position added by an interval β (t) exposed in an area where readout of an image signal at each time is not performed. The upper limit of the position that is actually exposed is shown.

  When attention is paid between the time T4 'and T4, the region indicated by the interval β (t) is exposed in a state where no image signal is read out. As shown in the figure, the exposure time in the region where the image signal is not read increases from 0 at the lower end of the image sensor 3 to T5-T5 'at the upper end of the image sensor 3.

  Therefore, a method for solving these problems will be described with reference to FIGS. 12 (c) and 13 (c).

  As described with reference to FIG. 12B, the light ray C emitted from the lower end of the exit pupil of the imaging lens 1 leaks from the lower end of the blade group 230 and reaches the pixels in the row where the still image readout scan has not yet reached. Incident light affects the image signal.

  Therefore, even if light leaks from the lower end of the blade group 230, the still image read scanning is completed so that the pixels that have not been read out of the image are outside the region where the leaked light from the blade group 230 reaches. The incident light may be incident on a pixel in a certain row. Specifically, the lower end of the blade group 230 may be controlled to be positioned below the image signal readout line by a predetermined interval α (t) in the direction perpendicular to the optical axis direction.

The interval α (t) is D for the exit pupil diameter of the imaging lens 1, L for the exit pupil of the imaging lens 1 and the imaging element, x for the distance between the blade group 230 and the imaging element, and the optical axis and image of the imaging lens 1. If the distance of the signal reading position is h (t),
α (t) = x (D / 2−h (t)) / L
It is represented by

  This state will be described with reference to FIG. An alternate long and short dash line is an image signal readout line, and an alternate long and two short dashes line indicates the upper limit of the position of the blade group 230 controlled to be at a position lower than the image signal readout line by an interval α (t).

  That is, if the position of the tip of the blade group 230 is below the two-dot chain line at each time, the region where the image signal is not read out from the image signal readout line is not exposed.

  Therefore, by maintaining the above-described predetermined distance between the image signal readout line and the tip of the blade group 230, it is possible to perform the charging operation of the blade group 230 in parallel with the readout of the image signal.

  Further, the interval α (t) between the image signal readout line and the tip of the blade group 230 increases from 0 at time T3 to γ at time T5. Note that γ is the distance between the upper end of the image sensor and the blade group 230 for shielding the upper end of the image sensor.

  Next, the control of the blade group 230 when performing the charging operation while maintaining a predetermined distance between the image signal readout line and the blade group 230 will be described.

  FIG. 14 is a diagram showing the relationship between the power supply voltage detected by the voltage detection means 91 and the opening speed of the blade group 230.

  As shown in FIG. 14, the opening speed of the blade group 230 increases as the voltage increases, and the opening speed of the blade group 230 changes from the lowest speed VA at the voltage A to the highest speed VC at the voltage C.

  FIG. 15 is a diagram showing the readout position of the image signal of the image sensor 3 and the position of the tip of the blade group 230 in the present embodiment. In FIG. 15, lines A, B, and C indicate the positions of the tips of the blade group 230 at time T when the detected power supply voltages are voltages A, B, and C, respectively.

  When the detected power supply voltage is the voltage C, the position of the tip of the blade group 230 at the time T5 when the image signal reading is finished must be set to a position separated from the upper end of the image sensor 3 by the interval γ or more. Therefore, the time when the blade group 230 starts the opening operation (start timing of the charging operation) is set to T6. At this time, the time for the tip of the blade group 230 to reach the upper end of the image sensor 3 is TC. Further, as shown in FIG. 15, when the detected power supply voltages are voltages A and B, the position of the tip of the blade group 230 at the time T is greater than or equal to the interval γ from the upper end of the image sensor 3 as in the case of the voltage C. It will be in a distant position.

  That is, the start timing of the charging operation is set so as to satisfy the following conditions. (1) The charging operation is started after the image signal reading operation is started and before the charge reading of the image sensor of the image signal is completed. (2) During the charging operation, the blade group opens the opening in a state where the tip of the blade group is separated from the image signal reading position by a predetermined distance.

  Therefore, since the position of the tip of the blade group 230 exists below the two-dot chain line regardless of the power supply voltage, the light leaked from the portion where the blade group 230 is open has not yet reached the still image readout scanning. The incident on the pixels in the row does not affect the image signal.

Also, moving image shooting or live view shooting can be started from TA, TB, and TC when the opening operation of the blade group 230 ends. In FIG. 15, lines A ′, B ′, and C ′ are the cases where the opening operation of the blade group 230 is started after the reading of the image signal is completely completed, and the detected power supply voltage is the voltage A. , B, and C, the position of the tip of the blade group 230 at time T is shown. As shown in FIG. 15, TA, TB, and TC at which the opening operation of the blade group 230 ends are earlier than the times TC ^′ , TB ^′ , and TA ^{′ at} which the opening operation of the blade group 230 ends. Accordingly, it is possible to shorten the time until the imaging operation is started again. As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

2 focal plane shutter 3 imaging device 100 imaging device 201 shutter base plate 201d opening 202 blade drive member 203 charge member 230 blade group

Claims (4)

An image sensor that photoelectrically converts a subject image to generate an image signal;
A focal plane shutter that is disposed in front of the image sensor and that switches between a light shielding state that shields the image sensor by moving a blade group and an exposure state that exposes the image sensor ;
The moving direction of the blade group when the imaging element switches the reading scanning direction of the image signal and the focal plane shutter switches from the light shielding state to the exposure state is set to the same direction,
Before the readout scan of the image signal is completed, the focal plane shutter starts to move the blade group for switching the imaging element from the light shielding state to the exposure state,
The focal plane shutter moves the blade group so that a region where the image signal is not read out is not in the exposure state . The imaging apparatus according to claim 1, wherein the focal plane shutter moves the blade group so that a part of a region where the image signal is read out is in the light shielding state . The imaging apparatus according to claim 2, wherein a size of the region in the light shielding state among regions where the image signal is read is changed depending on a reading position of the image signal. The focal plane shutter includes a shutter base plate having an opening, a blade group that opens and closes the opening and adjusts exposure to the image sensor, a blade driving member that drives the blade group, and the blade driving member. The imaging apparatus according to claim 1, further comprising: a drive spring that biases and a charge member that charges the drive spring.