JP2014010390A - Imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging device which achieves the control corresponding to an actual state of a shutter during continuous shooting.SOLUTION: An imaging device includes: a shutter running a front curtain and a rear curtain with the power of a motor; an imaging unit for continuously performing photographing operation in an exposure time controlled by the shutter; a temperature detection unit for acquiring a temperature of the motor; and a controller decreasing a value of a constant current supplied to the motor according to a temperature rise.

Description

  The present invention relates to an imaging apparatus.

  2. Description of the Related Art Conventionally, in a mechanical shutter of a compact camera, it has been proposed to change a constant current value supplied to a motor in accordance with temperature in order to keep the opening characteristic of the shutter constant.

Utility Model Registration No.25212261

  When continuous shooting is performed with an imaging apparatus, it is required that the mechanical shutter be stably operated with the same exposure time during the continuous shooting period. In general, the number of continuous shots of the imaging apparatus is determined uniformly within a range in which the same exposure time can be ensured under the strictest usage environment in consideration of the specifications of the mechanical shutter. Therefore, if control is performed in consideration of the actual state of the shutter, there is room for longer continuous shooting.

  An image pickup apparatus as an example of the present invention includes a shutter unit that drives a front curtain and a rear curtain with the power of a motor, an image pickup unit that continuously performs a shooting operation with an exposure time controlled by the shutter unit, and a motor temperature. A temperature detection unit to be acquired and a control unit that decreases a constant current value supplied to the motor in accordance with a rise in temperature.

  According to the present invention, control according to the actual state of the shutter can be performed during continuous shooting.

The figure which shows the structural example of the electronic camera in one Embodiment. The figure which shows the front curtain and rear curtain of the shutter part Flow chart showing an example of controlling the constant current value of the motor during continuous shooting The figure which shows the example of the temperature change of the motor at the time of continuous shooting

<Description of One Embodiment>
FIG. 1 is a diagram illustrating a configuration example of an electronic camera according to an embodiment, which is an example of an imaging apparatus.

  An electronic camera 100 according to one embodiment includes a photographing lens 11, a shutter unit 12, an imaging unit 13, a temperature detection unit 14, a posture detection unit 15, a pressure detection unit 16, a camera microcomputer 17, and each unit. The power supply 18 which supplies electric power, the electric current control part 19, the memory 20, the display part 21, media I / F22, and the operation part 23 which receives operation from a user are provided. The shutter unit 12, the imaging unit 13, the temperature detection unit 14, the attitude detection unit 15, the pressure detection unit 16, the current control unit 19, the memory 20, the display unit 21, the media I / F 22, and the operation unit 23 are respectively connected to the camera microcomputer 17. It is connected.

  The photographing lens 11 is composed of a plurality of lenses including, for example, a zoom lens and a focus lens. For the sake of simplicity, FIG. 1 shows the photographing lens 11 as a single lens.

  The shutter unit 12 is a focal plane shutter disposed between the photographing lens 11 and the imaging unit 13. The shutter unit 12 changes the light shielding state and the exposure state of the imaging unit 13 by driving shutter blades (front curtain and rear curtain). Note that the shutter unit 12 can mechanically adjust the exposure time of the imaging unit 13 by changing the travel interval between the front curtain and the rear curtain.

  In one embodiment, the shutter unit 12 has two motors 12a and 12b for the front curtain and the rear curtain, and the front curtain and the rear curtain are directly driven by the power of the motors 12a and 12b, respectively. . In one embodiment, the shutter unit 12 executes driving and returning (charging) of the front curtain by driving one motor 12a, and executing driving and charging of the rear curtain by driving the other motor 12b, respectively. Yes.

  FIG. 2 is a view showing a front curtain and a rear curtain of the shutter unit 12. The front curtain 31 is driven by moving the lever 34a in the groove cam 33a by the power of the motor 12a. Similarly, the rear curtain 32 is driven by moving the lever 34b in the groove cam 33b by the power of the motor 12b.

  FIG. 2 shows a state in which the shutter unit 12 is charged. The opening 35 of the shutter unit 12 is shielded by the front curtain 31, and the rear curtain 32 is positioned above the opening 35. When opening the shutter unit 12, the front curtain 31 is moved and moved downward. Then, when the shutter unit 12 is closed, the rear curtain 32 may be run to shield the opening 35 of the shutter unit 12 (the illustration of the open state and the closed state of the shutter unit 12 is omitted).

  At the time of exposure, the front curtain 31 moves in a direction urged by a stopper spring (not shown) when opened, while the rear curtain moves in a direction in which the stopper spring (not shown) opens. 32 moves. If the motors are controlled with the same constant current value, there may be variations in travel between the front curtain 31 and the rear curtain 32, so that the motors of the shutter unit 12 can be controlled to be driven with different constant current values.

  Returning to FIG. 1, the imaging unit 13 is a module that images (shoots) an image of a subject formed by a light beam incident through the photographing lens 11 and the shutter unit 12. For example, the imaging unit 13 includes an imaging device that performs photoelectric conversion, and a signal processing circuit that performs analog signal processing, A / D conversion processing, and the like on the output of the imaging device.

  Note that the image sensor of the imaging unit 13 has an electronic shutter function. In the electronic shutter, the imaging unit 13 controls the timing from the reset operation of the charge accumulated in the photoelectric conversion unit of the image sensor to the operation of reading the charge accumulated in the photoelectric conversion unit after the reset, so that the imaging unit 13 has a predetermined exposure time. You can get an image with

  Here, the imaging unit 13 captures a still image for recording accompanied by recording in a nonvolatile storage medium in accordance with an imaging instruction from the operation unit 23. At this time, the imaging unit 13 can also take still images continuously. In addition, the imaging unit 13 captures images for observation (through images) at predetermined time intervals during standby for capturing. The through-image data acquired in time series is used for moving image display (live view display) on the monitor and various arithmetic processes by the camera microcomputer 17.

  The temperature detection unit 14 is a temperature sensor (thermistor, digital temperature sensor, etc.) disposed in the vicinity of the motor of the shutter unit 12 and detects the temperature in the vicinity of the motor as the motor temperature. The temperature detector 14 may be arranged in the vicinity of the front curtain motor 12a and the rear curtain motor 12b.

  The posture detection unit 15 determines a shooting posture in which the electronic camera 100 is held in a normal position and a vertical shooting posture in which the electronic camera 100 is held with the right hand side or the left hand side facing up. For example, the posture detection unit 15 includes a triaxial acceleration sensor and a tilt switch.

  The pressure detection unit 16 is a known electric barometer, for example, and detects the pressure around the electronic camera 100.

  The camera microcomputer 17 is a processor that comprehensively controls the operation of the electronic camera 100. For example, the camera microcomputer 17 controls autofocus (AF) and automatic exposure (AE) using a through image signal. In addition, the camera microcomputer 17 performs various types of image processing (for example, color space conversion processing, gradation conversion processing, white balance adjustment processing, noise removal processing, and contour enhancement processing) on the image data.

  Moreover, the camera microcomputer 17 in one embodiment controls the operation of the shutter unit 12 according to the temperature of the motor, the photographing posture, and the atmospheric pressure as an example of the control unit. A control example of the shutter unit 12 by the camera microcomputer 17 will be described later.

  The current control unit 19 controls the constant current value supplied from the power source 18 to each of the motors 12 a and 12 b in accordance with an instruction from the camera microcomputer 17.

  The memory 20 stores a program executed by the camera microcomputer 17 and various data necessary for this program. For example, the memory 20 is configured by a nonvolatile flash memory.

  The display unit 21 is a display device that displays various images. For example, the display unit 21 performs moving image display (live view display) using a through image under the control of the camera microcomputer 17. The display unit 21 can also display various types of shooting information superimposed on the through image under the control of the camera microcomputer 17.

  The media I / F 22 has a connector for connecting a non-illustrated nonvolatile storage medium (hard disk, memory card, etc.). Then, the media I / F 22 executes writing / reading of data (recording image) with respect to the storage medium connected to the connector.

  Hereinafter, an operation example of the electronic camera in one embodiment will be described. First, operations of the shutter unit and the imaging unit at the time of shooting standby and when shooting a recording image will be briefly described. The following control is executed by the camera microcomputer 17.

  In one embodiment, when the electronic camera 100 is in a shooting standby state, the shutter unit 12 is always opened, and the imaging unit 13 is irradiated with a light beam that passes through the shooting lens 11. In this photographing standby state, the imaging unit 13 outputs a through image signal at predetermined time intervals by the electronic shutter.

  In addition, when a photographing instruction (for example, full pressing operation of the release button) is received from the operation unit 23, the electronic camera 100 captures a recording image. At this time, the camera microcomputer 17 charges the front curtain 31 and the rear curtain 32 and temporarily shields the opening 35 of the shutter unit 12 by the front curtain 31. When the opening 35 of the shutter unit 12 is shielded, the image sensor is reset. Thereafter, the opening 35 of the shutter unit 12 is opened by the traveling of the front curtain 31, and when a predetermined exposure time has elapsed since the traveling of the front curtain 31, the opening 35 of the shutter unit 12 is again shielded by the traveling of the rear curtain 32. At this time, the imaging unit 13 outputs a recording image signal based on the light beam received during the period (exposure time) when the opening 35 of the shutter unit 12 is open.

  When continuous shooting is performed, the above-described recording image shooting operation is repeatedly executed while a shooting instruction (for example, full-press operation of the release button) continues.

  Next, the control of the shutter unit by the camera microcomputer 17 will be described in detail. The camera microcomputer 17 in one embodiment controls the constant current value supplied to each motor via the current control unit 19 and adjusts the traveling speed of the front curtain 31 and the rear curtain 32 to be substantially constant. At this time, the camera microcomputer 17 sets constant current values of the motors 12a and 12b based on the following parameters.

(1: Motor temperature)
When the temperature of the motor of the shutter unit 12 increases, the torque and rotation speed of the motor increase, and the travel speed of the shutter blades increases as compared to the low temperature. Therefore, the camera microcomputer 17 performs control to lower the constant current value supplied to the motor as the temperature of the motor increases.

  Note that the shorter the shutter speed (exposure time), the greater the number of times the shutter blades travel per hour. Therefore, during continuous shooting, the motor temperature is more likely to increase as the shutter time is shorter, and the motor temperature is less likely to increase as the shutter time is longer.

  Also, the higher the constant current value of the motor, the greater the amount of heat generated by the motor. Therefore, during continuous shooting, the higher the motor constant current value, the easier the motor temperature rises, and the lower the motor constant current value, the less likely the motor temperature rises.

(2: Shooting posture)
The traveling speed of the shutter blades can be changed depending on the shooting posture of the electronic camera 100 (normal position shooting, vertical position shooting). The direction in which the shutter blades descend is the gravitational direction when photographing in the normal position, but the direction in which the curtain descends is perpendicular to the gravitational direction (parallel to the ground) when photographing in the vertical position. Therefore, when shooting at the normal position, the traveling speed of the shutter blades is faster due to the gravitational acceleration than when shooting at the vertical position. Therefore, the camera microcomputer 17 of one embodiment performs control to increase the constant current value supplied to the motor as needed in the case of vertical position shooting as compared to the case of normal position shooting.

(3: atmospheric pressure)
For example, when climbing, the sliding characteristics of the shutter unit 12 may change depending on whether the pressure is low (near the top) or high (near the foot). When the atmospheric pressure is low, the sliding characteristics of the shutter unit 12 are high (easy to slide), and the traveling speed of the shutter blades is relatively high. On the other hand, when the atmospheric pressure is high, the sliding characteristics of the shutter unit 12 are low (sliding is difficult), and the traveling speed of the shutter blades is relatively slow. Therefore, when the ambient atmospheric pressure is low, the camera microcomputer 17 of one embodiment performs control to reduce the constant current value supplied to the motor. Further, when the electronic camera 100 has a waterproof function, the pressure detection unit 16 may detect the water pressure. Since the water pressure applied to the electronic camera 100 changes depending on the depth, the camera microcomputer 17 may control the constant current value supplied to the motor in accordance with the change.

  Here, when the above control is performed, for example, the manufacturer generates a data table by obtaining a correspondence relationship between each parameter such as the motor temperature, photographing posture, atmospheric pressure, and water pressure and the travel speed of the shutter blades through experiments. The data table is stored in the memory 20 in advance. And the camera microcomputer 17 should just set the constant current value supplied to a motor via the current control part 19 with reference to said data table.

  Further, at the time of continuous shooting, the camera microcomputer 17 sequentially detects each parameter such as the temperature of the motor, and changes the constant current value supplied to the motor in accordance with a change in the parameter (for example, an increase in the temperature of the motor). Needless to say, these constant current values are set separately for the motor 12a of the front curtain 31 and the motor 12b of the rear curtain 32.

  FIG. 3 is a flowchart showing an example of control of the constant current value of the motor during continuous shooting when the parameter is temperature. The process of FIG. 3 is started by the camera microcomputer 17 when a shooting instruction (for example, full pressing operation of the release button) is accepted.

  Step # 101: The camera microcomputer 17 initializes a constant current value supplied to the motor according to the temperature of the motor.

  Step # 102: The camera microcomputer 17 causes the front curtain 31 and the rear curtain 32 of the shutter unit 12 to travel at a predetermined time interval and causes the imaging unit 13 to capture a recording image.

  Step # 103: The camera microcomputer 17 determines whether or not there is an instruction to end continuous shooting (for example, release of the release button). If the above requirement is satisfied (YES side), the camera microcomputer 17 ends the continuous shooting. On the other hand, if the above requirement is not satisfied (NO side), the process proceeds to # 104.

  Step # 104: The camera microcomputer 17 monitors the temperature of the motor, and again obtains a constant current value to be supplied to the motor under the current temperature condition.

  For example, when the temperature of the motor significantly increases during continuous shooting, the camera microcomputer 17 refers to the data table, and a constant current value lower than the current value is calculated.

  Step # 105: The camera microcomputer 17 determines whether or not the currently set constant current value is different from the constant current value obtained in # 104. If the above requirement is satisfied (YES side), the process proceeds to # 106. On the other hand, if the above requirement is not satisfied (NO side), the process proceeds to # 107.

  Step # 106: The camera microcomputer 17 instructs the current controller 19 to change the constant current value to the value obtained in # 104. Then, the current control unit 19 changes the constant current value supplied to the motor when shooting for one frame is completed.

  For example, if the motor temperature rises significantly during continuous shooting, the constant current value decreases to the value calculated in # 104 in # 106. Therefore, in this case, the traveling speed of the shutter blades is adjusted according to the temperature rise, and the temperature rise of the shutter unit 12 is also suppressed.

  Step # 107: The camera microcomputer 17 determines whether or not the motor temperature has exceeded the photographing stop threshold. If the above requirement is satisfied (YES side), the process proceeds to # 108. On the other hand, if the above requirement is not satisfied (NO side), the process returns to # 102 and the camera microcomputer 17 repeats the above processing.

  Step # 108: The camera microcomputer 17 stops the operation of the shutter unit 12. At this time, the camera microcomputer 17 may completely end the continuous shooting. Alternatively, the camera microcomputer 17 at # 108 may fix the shutter unit 12 in the open state and switch the imaging unit 13 to electronic shutter control to continue imaging of the subject. Above, description of the flowchart of FIG. 3 is complete | finished.

  FIG. 4 is a diagram illustrating an example of a motor temperature change during continuous shooting. FIG. 4A is a diagram showing a change in the temperature of the motor over time, the solid line shows the temperature change when the constant current value is controlled, and the alternate long and short dash line shows the temperature change when the constant current value is not controlled. FIG. 4B is a diagram showing the time variation of the constant current value. The solid line indicates the constant current value when the constant current value is controlled, and the alternate long and short dash line indicates the constant current value when the constant current value is not controlled. Show. In the example of FIG. 4, it is assumed that the setting for the shutter speed during continuous shooting, the shooting posture, and the pressure are both constant.

  In FIG. 4A, the temperature T0 indicates the initial temperature of the motor at the start of continuous shooting. In FIG. 4B, a constant current value I0 indicates a constant current value at the start of continuous shooting. Temperatures T1, T2, and T3 indicate temperatures at which the constant current value is changed. The temperature TE indicates a threshold temperature for stopping shooting. When the motor temperature reaches the temperature TE, continuous shooting is stopped. When controlling the constant current value, the camera microcomputer 17 performs control to decrease the constant current value to I1, I2, and I3 when the motor temperature changes to T1, T2, and T3. On the other hand, when the constant current value is not controlled, the constant current value remains constant at I0. When the constant current value is controlled (decreased), as shown by the solid line in FIG. 4A, the gradient of temperature increase becomes smaller than that of the one-dot chain line where the constant current value does not change.

  FIG. 4C is a diagram showing the change over time of the number of shots. When the constant current value is not controlled, the temperature of the motor becomes the temperature TE at time t3, and the number of shots is Y. On the other hand, when the constant current value is controlled, the time for the motor temperature to reach the temperature TE is increased to t4, and the number of shots is X. By controlling the constant current value, the time during which continuous shooting can be performed becomes longer, and the number of shots can be increased by (XY). Furthermore, since the traveling speeds of the front curtain 31 and the rear curtain 32 are adjusted to be constant in consideration of the actual state of the shutter, continuous exposure shooting has less variation in exposure time than when the constant current value is not controlled. Is possible.

<Modification of one embodiment>
In one embodiment, the camera microcomputer 17 may estimate the number of continuous shots that can be taken before the start of continuous shooting until the motor temperature reaches the shooting stop threshold. Then, the camera microcomputer 17 may determine the upper limit of the number of images that can be continuously shot based on the estimated value.

  For example, the camera microcomputer 17 can determine the constant current value supplied to the motor by acquiring the initial temperature of the motor. If the shutter speed at the time of continuous shooting and the constant current value of the motor are known, the camera microcomputer 17 can estimate the temperature increase with respect to the number of continuous shooting. Thereby, the camera microcomputer 17 can estimate the number of continuous shots from the initial temperature T0 to the temperature T1 at which the constant current value is changed.

  The camera microcomputer 17 can estimate the number of continuous shots from the temperature T1 to the temperature T2 because the temperature T1, the shutter speed during continuous shooting, and the constant current value of the motor are all known. By repeating the above processing, the camera microcomputer 17 can estimate the number of continuous shots from the initial temperature T0 to the threshold temperature TE.

  In the above case, the camera microcomputer 17 displays the upper limit of the number of continuous shots based on the estimated value on the display unit 21 as one piece of shooting information before the start of continuous shooting. Thereby, in the configuration of one embodiment, the user can grasp in advance the number of images that can be continuously shot.

<Supplementary items of the embodiment>
(Supplement 1): In the above embodiment, the example in which the determination of the change of the constant current value is performed for each frame has been described. However, in the present invention, the above determination may be performed every several frames, or the continuous shooting frame. You may make it perform the said determination for every predetermined period regardless of a number.

  (Supplement 2): In the implementation of the present invention, the change of the constant current value of the motor due to the photographing posture and the change of the constant current value of the motor due to the atmospheric pressure or water pressure may be omitted.

  From the above detailed description, features and advantages of the embodiments will become apparent. It is intended that the scope of the claims extend to the features and advantages of the embodiments as described above without departing from the spirit and scope of the right. Further, any person having ordinary knowledge in the technical field should be able to easily come up with any improvements and modifications, and there is no intention to limit the scope of the embodiments having the invention to those described above. It is also possible to use appropriate improvements and equivalents within the scope disclosed in.

DESCRIPTION OF SYMBOLS 11 ... Shooting lens, 12 ... Shutter part, 12a, 12b ... Motor, 13 ... Imaging part, 14 ... Temperature detection part, 15 ... Attitude detection part, 16 ... Pressure detection part, 17 ... Camera microcomputer, 18 ... Power supply, 19 ... Current control unit, 20 ... memory, 21 ... display unit, 22 ... media I / F, 23 ... operation unit, 100 ... electronic camera

Claims (8)

A shutter section for driving the front curtain and the rear curtain with the power of the motor;
An imaging unit that continuously performs a shooting operation with an exposure time controlled by the shutter unit;
A temperature detector for acquiring the temperature of the motor;
A control unit for reducing a constant current value supplied to the motor in accordance with an increase in the temperature;
An imaging apparatus comprising: The imaging device according to claim 1,
The temperature detector is disposed in the vicinity of the motor that drives the front curtain and the rear curtain,
The image pickup apparatus, wherein the control unit makes a constant current value supplied to the motor for running the front curtain different from a constant current value supplied to the motor for running the rear curtain. In the imaging device according to claim 1 or 2,
The control unit is an imaging device that stops the operation of the shutter unit when the temperature exceeds a threshold value. In the imaging device according to any one of claims 1 to 3,
The control unit is an image pickup apparatus that determines the number of continuous shots that can be taken before the temperature reaches a threshold value based on the setting of the exposure time and the temperature before the start of shooting. The imaging apparatus according to claim 4,
An imaging apparatus further comprising a display unit that displays the number of continuous shots determined by the control unit. In the imaging device according to any one of claims 1 to 5,
The control unit is an image pickup apparatus that continues a photographing operation at the exposure time by electronic shutter control of the image pickup unit when the temperature exceeds a threshold value. The imaging apparatus according to any one of claims 1 to 6,
A posture detection unit that detects the shooting posture is further provided.
The said control part is an imaging device which changes the said constant current value according to the said imaging | photography attitude | position. In the imaging device according to any one of claims 1 to 7,
A pressure detection unit for detecting pressure;
The said control part is an imaging device which changes the said constant current value according to the said pressure.

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