JP2013033165A - Imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging apparatus capable of suppressing heat generation of an electromagnet when performing long-time exposure, and also suppressing reduction in exposure accuracy when performing high speed exposure.SOLUTION: In a digital camera 1, a front curtain 410 and a rear curtain 420 are moved to an exposure start position by release operation, have a driving force charged in a travel direction, and are suction-held by a front curtain electromagnet 413 and a rear curtain electromagnet 423 (steps S1 to S4). Next, exposure is started by turning off energization to the front curtain electromagnet 413 and making the front curtain 410 travel, and the supply power to the rear curtain electromagnet 423 is reduced when performing long-time exposure (steps S5 to S9).

Description

  The present invention relates to an imaging apparatus including a focal plane shutter.

  Among the focal plane shutters used in conventional imaging devices, there is an electromagnet release type focal plane shutter. In this electromagnet release type focal plane shutter, the front curtain and the rear curtain charged with driving force in the running direction are attracted and held at the exposure start position by the energized front curtain electromagnet and the rear curtain electromagnet, respectively, and then the front curtain electromagnet Exposure is started by turning off the power to the front curtain and running the front curtain.

  As a method of controlling the electromagnet release type focal plane shutter, for example, a method is disclosed in which the power supplied to both electromagnets is reduced after the front curtain and rear curtain move from the monitoring position to the exposure start position (Patent Document). 1). As a result, even when the exposure time (exposure time) is longer than usual exposure, it is possible to suppress the heat generation of the electromagnet.

  However, if the power supplied to the electromagnet is reduced, the attractive force for the front curtain and the rear curtain becomes unstable. Therefore, when exposure is performed with an exposure time that is much shorter than usual (high-speed exposure at a high speed), uneven exposure (a condition in which the exposure amount becomes uneven due to a difference in running characteristics between the front curtain and the rear curtain, and lightness can be shaded in the running direction). Has occurred, and there has been a problem that the exposure accuracy is lowered.

  The present invention has been made in view of such conventional problems, and an imaging apparatus capable of suppressing heat generation of an electromagnet in the case of long-time exposure and suppressing a decrease in exposure accuracy in the case of high-speed second-time exposure. The purpose is to provide.

  As a result of intensive studies, the present inventors have adopted the following imaging device in order to solve the above-described problems.

The imaging apparatus of the present invention
The front curtain and rear curtain charged with driving force in the traveling direction are attracted and held at the exposure start position by the energized front curtain electromagnet and rear curtain electromagnet, respectively, and the front curtain electromagnet is turned off to turn off the front curtain In an imaging device including a focal plane shutter that starts exposure by running
Comprising energization control means for controlling energization to the front curtain electromagnet and the rear curtain electromagnet;
The energization control means supplies power to the rear curtain electromagnet between the time when the exposure time elapses after the energization of the front curtain electromagnet is turned off when the exposure time is longer than usual. It is characterized by reducing power.

  In the image pickup apparatus of the present invention, the power supplied to the rear curtain electromagnet is reduced in the case of long-second exposure. Therefore, in the case of high-speed second time exposure, the supply power is not reduced, so that exposure unevenness does not occur. Therefore, the imaging apparatus of the present invention can suppress the heat generation of the electromagnet in the case of long-time exposure, and can suppress the decrease in exposure accuracy in the case of high-speed second-time exposure.

It is a block diagram which shows a part of structure of the digital camera of one embodiment of this invention. It is a block diagram which shows the structure of the focal plane shutter of the embodiment. It is a flowchart which shows the content of the exposure control of the focal plane shutter of the embodiment. It is a figure which shows an example of a structure of the shutter control circuit of the embodiment. It is a figure which shows an example of the electric power supplied to the front curtain electromagnet and the rear curtain electromagnet of the embodiment. It is the figure which compared the temperature rise of the rear curtain electromagnet by the presence or absence of the reduction | decrease in the electric power supplied to a rear curtain electromagnet. It is a figure which shows an example of the measurement point of the exposure nonuniformity in a longitudinally running type focal plane shutter.

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

  FIG. 1 is a block diagram showing a part of the configuration of a digital camera 1 (imaging device) according to an embodiment of the present invention.

  The digital camera 1 is provided with an image processing circuit (image processing device). This image processing circuit temporarily stores a CCD (solid-state imaging device) 101 for photoelectrically converting an optical image, an F / E (front end) -IC 102 for preprocessing an image signal from the CCD 101, and image data. SDRAM 103 to be used.

  The image processing circuit includes a digital camera processor 104 as a main arithmetic control device that performs various processes on image data from the F / E-IC 102.

  The image processing circuit further includes a SUBCPU 105 as a sub-operation control device, a built-in memory 107, an LCD driver 108, and a video AMP 109.

  An operation signal from the operation key unit 11 is input to the SUBCPU 105. The operation key unit 11 is a key circuit operated by a user, and includes various switches such as a power switch, a display switch, and a release switch.

  The SUBCPU 105 is a CPU in which a ROM and a RAM are built in one chip, and outputs an output signal from the operation key unit or the like to a later-described CPU block 104-3 as user operation information. Although not shown, the SUBCPU 105 controls time by communicating with a timer that counts time.

  The F / E-IC 102 includes a CDS 102-1 that performs correlated double sampling for image noise removal, an AGC 102-2 that performs gain adjustment, an A / D 102-3 that performs digital signal conversion, and a TG 102 that generates a drive timing signal. -4.

  The SDRAM 103 temporarily stores image data when the digital camera processor 104 performs various processes on the image data. The image data to be stored is, for example, “RAW-RGB image data” in the state in which the white balance setting and the gamma setting are performed by the CCD 1 signal processing block 104-1 from the CCD 101 via the F / E-IC 102. “YUV image data” in which the luminance data and color difference data have been converted in the signal block 104-2, “JPEG image data” compressed in JPEG in the JPEG CODEC block 104-7, and the like. The built-in memory 107 is a memory for enabling the captured image data to be stored.

  The digital camera processor 104 includes a CCD1 signal processing block 104-1 that performs white balance setting and gamma setting on the output data of the F / E-IC 102 and supplies a vertical synchronization signal and a horizontal synchronization signal to the TG 1024.

  Further, the digital camera processor 104 includes a CCD 2 signal processing block 104-2 that performs conversion into luminance data and color difference data by filtering processing, a CPU block 104-3 that controls the operation of each part of the apparatus, data necessary for control, and the like. Is stored in the local SRAM 104-4.

  The digital camera processor 104 also includes a USB block 104-5 that performs USB communication with an external device such as a personal computer, a serial block 104-6 that performs serial communication with an external device such as a personal computer, and a JPEG CODEC block 104 that performs JPEG compression / decompression. -7, a RESIZE block 104-8 for enlarging / reducing the size of the image data by interpolation processing, and a TV signal display block 104-9 for converting the image data into a video signal for display on an external display device such as a liquid crystal monitor or TV. , A memory card controller block 104-10 for controlling a memory card for recording photographed image data, an I2C block 104-11, and an audio block 104-12.

  The LCD driver 108 is a drive circuit that drives the LCD monitor 115, and also has a function of converting the video signal output from the TV signal display block 104-9 into a signal for display on the LCD monitor 115. The LCD monitor 115 is a monitor for monitoring the state of a subject before photographing, confirming a photographed image, displaying image data recorded in a memory card or the built-in memory 107, and the like. The video AMP 109 is an amplifier for 75Ω impedance conversion of the video signal output from the TV signal display block 104-9. The video jack 110 is a jack for connecting to an external display device such as a TV.

  A speaker 113 is connected to the audio block 104-12 via an audio CODEC 112. The audio CODEC 112 converts the audio data output from the audio block 104-12 into a signal that can be output from the speaker.

  The digital camera 1 also includes a strobe unit. The strobe unit includes a strobe light emitting unit 120 that emits light during strobe shooting, and a strobe circuit (LED strobe light emission control circuit) 106 as a brightness control device that controls the strobe light emitting unit 120. The strobe circuit 106 is controlled by the CPU block 104-3 to emit illumination light from the strobe light emitting unit 120. The CPU block 104-3 is also configured to control the distance measuring unit 5.

  The digital camera 1 further includes an acceleration sensor 111 (acceleration detecting means of the present invention). The acceleration sensor 111 can basically measure acceleration, and can also detect the direction of gravity, that is, measure the degree of inclination with respect to the direction of gravity. For this reason, the acceleration sensor 111 functions as an inclination detection means. The acceleration sensor 111 is mounted on a printed circuit board, and outputs acceleration data and temperature information in two orthogonal axes xy directions to the I2C block 104-11.

  The digital camera processor 104 serially communicates with the acceleration sensor 111 via the I2C block 104-11, calculates the tilt of the digital camera 1 from the acquired data, and displays the superimposed image on the LCD monitor 115 and the like. The calculation of the inclination is performed by the CPU block 104-3, for example.

  The digital camera 1 further includes a focal plane shutter 4 that performs exposure control. As shown in FIG. 2, the focal plane shutter 4 includes a front curtain 410 and a rear curtain 420, a front curtain driving member 411 and a rear curtain driving member 421, a front curtain biasing member 412 and a rear curtain biasing member 422, and a charge motor 430. , A front curtain electromagnet 413, a rear curtain electromagnet 423, and a shutter control circuit 440 are provided.

  The front curtain 410 and the rear curtain 420 are arranged on the front surface of the CCD 101 and run in a predetermined direction to perform exposure control. The front curtain driving member 411 and the rear curtain driving member 421 are members that drive the front curtain 410 and the rear curtain 420 in the traveling direction (predetermined direction). The front-curtain urging member 412 and the rear-curtain urging member 422 are members that urge the front-curtain drive member 411 and the rear-curtain drive member 421 in the traveling direction, and a compression spring or the like is used.

  The charge motor 430 charges the urging force of the front curtain urging member 412 and the rear curtain urging member 422 to return the front curtain 410 and the rear curtain 420 from the exposure end position to the monitoring position, or from the monitoring position to the exposure start position. It is to be moved. The front curtain electromagnet 413 and the rear curtain electromagnet 423 attract and hold the front curtain biasing member 412 and the rear curtain biasing member 422 charged with the biasing force, and fix the front curtain 410 and the rear curtain 420 at the exposure start position. It is.

  The shutter control circuit 440 controls the operation of the charge motor 430. Further, the shutter control circuit 440 controls the running and stopping of the front curtain 410 and the rear curtain 420 by switching on and off the energization of the front curtain electromagnet 413 and the rear curtain electromagnet 423 according to an instruction from the CPU block 104-3. . The CPU block 104-3 includes the energization control unit of the present invention.

  The contents of the exposure control of the focal plane shutter 4 in the digital camera 1 configured as described above will be described using the flowchart of FIG.

(Steps S1 to S2, S3)
When the release operation is performed, that is, when the release switch is turned on, the CPU block 104-3 energizes the front curtain electromagnet 413 and the rear curtain electromagnet 423 through the shutter control circuit 440 and energizes the charge motor 430.

(Step S4)
When the charge motor 430 is energized, the charge motor 430 charges the front curtain biasing member 412 and the rear curtain biasing member 422 at the monitoring position. For example, when the front curtain biasing member 412 and the rear curtain biasing member 422 are compression springs, the compression springs are extended to a predetermined length. As a result, the front curtain 410 and the rear curtain 420 are moved from the monitoring position to the exposure start position and charged with the driving force in the traveling direction, and are attracted and held by the front curtain electromagnet 413 and the rear curtain electromagnet 423, respectively.

  If the attractive force of the front curtain electromagnet 413 and the rear curtain electromagnet 423 is not sufficient at this time, the front curtain 410 and the rear curtain 420 run away without stopping at the exposure start position when a large impact is applied to the digital camera 1. There is a risk. Therefore, the CPU block 104-3 sets the amount of power supplied to the front curtain electromagnet 413 and the rear curtain electromagnet 423 through the shutter control circuit 440 so that the attractive force of the front curtain electromagnet 413 and the rear curtain electromagnet 423 is sufficient. Yes.

(Steps S5 to S6)
Next, the CPU block 104-3 turns off the energization to the front curtain electromagnet 413 through the shutter control circuit 440. As a result, the front curtain 410 travels toward the exposure end position, and exposure is started.

(Step S7)
Next, the CPU block 104-3 determines whether or not the exposure is long time exposure from the time when the release switch is on. In addition, long time exposure is exposure whose exposure time (exposure time) is longer than usual.

(Step S8)
If the CPU block 104-3 determines that the exposure is long time (YES in step S7), the CPU block 104-3 determines whether or not a predetermined time has elapsed since turning off the energization to the front curtain electromagnet 413 by the timer. To do.

(Step S9)
The CPU block 104-3 reduces the power supplied to the rear curtain electromagnet 423 through the shutter control circuit 440 when a predetermined time has elapsed after the energization of the front curtain electromagnet is turned off.

(Step S10)
Next, the CPU block 104-3 determines whether or not the exposure time has elapsed. This determination process is also performed when the determination result of step S7 is NO, that is, when the exposure is other than the long time exposure (high speed second exposure, normal exposure, low speed second exposure). The high-speed second exposure is exposure with a shorter exposure time than the long-second exposure, and the low-speed second exposure is exposure with a longer exposure time than the normal exposure.

(Steps S11 to S12)
If the CPU block 104-3 determines that the exposure time has elapsed (YES in step S10), the CPU block 104-3 turns off the energization to the rear curtain electromagnet 423. As a result, the rear curtain 420 travels toward the exposure end position, and the exposure ends.

(Step S13)
The CPU block 104-3 energizes the charge motor 430 through the shutter control circuit 440 when the exposure is completed and the transfer of the captured image is completed.

(Step S14)
When the charge motor 430 is energized, the charge motor 430 charges the front curtain biasing member 412 and the rear curtain biasing member 422 at the exposure end position. For example, when the front curtain biasing member 412 and the rear curtain biasing member 422 are compression springs, the compression springs are extended to a predetermined length. As a result, the front curtain 410 and the rear curtain 420 move from the exposure end position to the monitoring position and enter the monitoring state.

  As described above, in the digital camera 1 of the present embodiment, the power supplied to the rear curtain electromagnet 423 is reduced in the case of long-time exposure, so that the electromagnets (the front curtain electromagnet 413 and the rear curtain electromagnet 423) are reduced. Heat generation can be suppressed. Further, in the case of high-speed second exposure, since supply power is not reduced, exposure unevenness does not occur, so that a reduction in exposure accuracy can be suppressed.

  FIG. 4 shows an example of the configuration of the shutter control circuit 440. In the shutter control circuit 440, a front curtain Mg (front curtain electromagnet 413) and a rear curtain Mg (rear curtain electromagnet 423) are connected in parallel to VCC.

  A transistor Tr1 is connected between the leading curtain Mg and GND. A resistor Ra is connected between the transistor Tr1 and the CPU (CPU block 104-3). A resistor Rb is connected between the resistor Ra and the transistor Tr1 and between the transistors Tr1 and GND.

  Transistors Tr2 and Tr3 are connected in parallel between the rear curtain Mg and GND. A resistor Rc is connected between the transistor Tr2 and the CPU (CPU block 104-3). A resistor Rd is connected between the resistor Rc and the transistor Tr2 and between the transistor Tr2 and GND.

  A resistor R1 (current detection resistor) is connected between the rear curtain Mg and the transistor Tr3. A resistor Re is connected between the transistor Tr3 and the CPU (CPU block 104-3). A resistor Rf is connected between the resistor Re and the transistor Tr3 and between the transistor Tr3 and GND.

  4 will be described together with the flowchart of FIG. 3. In order to make the adsorption power of the front curtain Mg and the rear curtain Mg sufficient at the time of step S4 (charge completion) in FIG. The amount of power supplied to the front curtain Mg and the rear curtain Mg is set based on the potential difference and the resistance values of the front curtain Mg and the rear curtain Mg. Thereby, even if a large impact is applied to the digital camera 1, the runaway of the front curtain 410 and the rear curtain 420 can be prevented.

  In step S9 of FIG. 3, the potential difference between VCC and GND and the rear curtain are set so that the rear curtain Mg has an adsorption force that is lower than that in step S4 but has no problem with holding the rear curtain 420. The power supplied to the trailing curtain Mg is reduced by dividing the resistance value of Mg and R1.

  FIG. 5 shows an example of the amount of power supplied to the front curtain electromagnet 413 and the rear curtain electromagnet 423. FIG. 5 will be described together with the flowchart of FIG. 3. When a release operation is performed in the exposure control of the focal plane shutter 4 (step S1), the amount of power supplied to the front curtain electromagnet 413 and the rear curtain electromagnet 423 is set to 300 mW. Set to. This supplied power amount of 300 mW is the amount of power that can sufficiently attract the front curtain Mg and the rear curtain Mg at the time of charging completion (step S4), and even if a large impact is applied to the digital camera 1. The runaway of the front curtain 410 and the rear curtain 420 can be prevented.

  Next, the energization of the front curtain electromagnet 413 is turned off (0 mW) and exposure is started (steps S5 to S6). When the exposure is long time exposure, after a predetermined time t has elapsed, the amount of power supplied to the rear curtain electromagnet 423 is reduced to 100 mW (steps S7 to S9). The amount of power of 100 mW is an amount of power that causes no problem in holding the trailing curtain 420 even though the attractive force of the trailing curtain electromagnet 423 is reduced, and is an error level even when exposure unevenness occurs.

  In this state, after the exposure time has elapsed, the energization of the rear curtain electromagnet is turned off (0 mW), and the exposure ends (steps S10 to S12). By performing the exposure control as described above, for example, when the exposure time is 3 minutes, the temperature increase of the rear curtain electromagnet 423 can be suppressed as shown in FIG.

  FIG. 7 shows an example of measurement points of exposure unevenness in a longitudinal running type focal plane shutter. Allowable exposure unevenness varies depending on the exposure time. For example, when the exposure time is 1/2000 second, between the two points among the three points of the center point of the imaging area, the point A located above and below the center point, and the point B The exposure time difference is within 0.4 EV.

  An example of the predetermined time t shown in FIG. 5 (the time from the start of long-second exposure (turning off the energization to the front curtain electromagnet 413) to the reduction of the power supplied to the rear curtain electromagnet 423) will be described. The direction L is set to t = 5v or more, where v is the curtain speed at which the shutter curtains (front curtain 410 and rear curtain 420) travel. If the exposure time is t = 5v or more, the exposure unevenness becomes an error level.

  Examples of conditions for reducing the power supplied to the rear curtain electromagnet 423 include (1) when the exposure time is equal to or longer than the predetermined time t = 5v described above, and (2) when in the long-second shooting mode in the bulb mode. Is mentioned.

  In addition, when the shutter curtain travel characteristic is uneven due to the temperature characteristic of the shutter curtain, the internal temperature of the digital camera 1 is detected by using the temperature detection means, and the influence of the internal temperature causes the rear curtain electromagnet 423 to be affected. The supplied power may be reduced so that the suction holding force with respect to the trailing curtain 420 is not lost.

  For example, when the internal temperature of the digital camera 1 is T and the exposure time is t = 5v + | T−25 | * α (constant) or more, the supplied power is reduced. Alternatively, the power supply is reduced when the temperature exceeds a certain temperature and the exposure time is t = 5v + α (constant) or more.

  Also, at least one of the predetermined time t or the reduced power supply amount to the rear curtain electromagnet 423 may be set using the internal temperature. As a result, the loss of the attractive force of the rear curtain electromagnet 423 due to the influence of the internal temperature is suppressed. Therefore, exposure unevenness can be suppressed and a reduction in exposure accuracy can be prevented.

  In addition, the CPU block 104-3 calculates the amount of change in acceleration detected by the acceleration sensor 111, and the amount of change is between the time when the energization to the front curtain electromagnet 413 is turned off and the exposure time elapses. The power supplied to the rear curtain electromagnet 423 may be reduced when it becomes larger than the predetermined change amount and then becomes smaller.

  In this case, since it becomes possible to prevent the rear curtain 420 from being released even when a large impact is applied to the digital camera 1, the exposure accuracy can be increased. As the acceleration detecting means, in addition to the acceleration sensor 111, a blur correction sensor, a horizontal display sensor, or a dedicated sensor may be used. In addition, when the change amount of acceleration is smaller than the predetermined change amount, the power supplied to the trailing curtain electromagnet 423 may be reduced without waiting for the predetermined time t to elapse.

  Further, the CPU block 104-3 may increase or decrease the supply power to the rear curtain electromagnet 423 in accordance with the change amount of acceleration and a predetermined change amount after reducing the supply power to the rear curtain electromagnet 423. In this case, the holding force of the rear curtain 420 can be changed in accordance with the change in the situation, so that the power can be reduced while ensuring an appropriate holding force for the rear curtain 420. Note that when the supply power is increased, the normal supply power may be restored.

  Further, the CPU block 104-3 may increase the power supplied to the rear curtain electromagnet 423 when the amount of change in acceleration becomes larger than the predetermined change after reducing the power supplied to the rear curtain electromagnet 423. . In this case, it is possible to reliably prevent the rear curtain 420 from being released even when a large impact is applied to the digital camera 1 again, and the exposure accuracy can be further increased. Note that when the supply power is increased, the normal supply power may be restored.

  As mentioned above, although the Example which concerns on this invention was illustrated, this Example does not limit the content of this invention. Various modifications can be made without departing from the scope of the claims of the present invention.

1 Digital camera (imaging device)
410 Front curtain 413 Front curtain electromagnet 420 Rear curtain 423 Rear curtain electromagnet 104-3 CPU block (energization control means)

Japanese Patent Laid-Open No. 2005-282897

Claims (5)

The front curtain and rear curtain charged with driving force in the traveling direction are attracted and held at the exposure start position by the energized front curtain electromagnet and rear curtain electromagnet, respectively, and the front curtain electromagnet is turned off to turn off the front curtain In an imaging device including a focal plane shutter that starts exposure by running
Comprising energization control means for controlling energization to the front curtain electromagnet and the rear curtain electromagnet;
The energization control means supplies power to the rear curtain electromagnet between the time when the exposure time elapses after the energization of the front curtain electromagnet is turned off when the exposure time is longer than usual. An imaging device characterized by reducing power. The imaging device according to claim 1,
Acceleration detecting means for detecting acceleration generated in the imaging apparatus is further provided,
The energization control unit calculates a change amount of the acceleration detected by the acceleration detection unit, and the change amount is predetermined after the energization to the front curtain electromagnet is turned off until the exposure time elapses. An image pickup apparatus, wherein power supplied to the rear curtain electromagnet is reduced when the change amount is larger than the change amount and then becomes smaller. The imaging device according to claim 2,
The energization control means, after reducing the power supplied to the rear curtain electromagnet, increases or decreases the power supplied to the rear curtain electromagnet according to the amount of change in acceleration and the predetermined amount of change. . The imaging device according to claim 3.
The energization control means increases the power supplied to the rear curtain electromagnet when the acceleration change amount becomes larger than the predetermined change amount after reducing the power supplied to the rear curtain electromagnet. Imaging device. In the imaging device according to any one of claims 1 to 4,
A temperature detecting means for detecting the internal temperature of the imaging device;
The energization control means turns off the energization to the front curtain electromagnet so that the suction holding force of the rear curtain electromagnet to the rear curtain is not lost under the influence of the internal temperature detected by the temperature detection means. The imaging apparatus is characterized in that at least one of a time from when the power is supplied until the power supply to the rear curtain electromagnet is reduced or a reduced power supply amount to the rear curtain electromagnet is set.