JP2005115146A - Electronic flash device, its control method and camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide control technique for an electronic flash to perform such control that a light detecting sensor is prevented from being saturated. <P>SOLUTION: The electronic flash device is equipped with an electronic flash means(302), a photometry means (115) having the light receiving sensor receiving reflected light by preliminary light emission and outputting the integrated value of received light quantity in a specified integration time, and control means (150, 301 and 350) controlling the preliminary light emission by the electronic flash means and the photometry means and also controlling regular light emission after the preliminary light emission based on the result of photometry by the photometry means. The control means sets the integration time of the light receiving sensor in accordance with the shutter speed of a focal plane shutter at the time of regular light emission in a flat light emitting mode. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a control technology for a strobe device of a camera.

  In strobe flash photography, a method of performing preliminary light emission prior to main light emission is known in order to determine an appropriate amount of light at the time of photography. In this method, the amount of light received by preliminary light emission is detected, and the amount of light emission of main light emission is determined.

  In this case, in the preliminary light emission, the light received by the light receiving sensor is the sum of the strobe light and the background light. For this reason, the received light is affected by the background light (hereinafter also referred to as “steady light”). Therefore, when the steady light is large, the output of the light receiving sensor is saturated and accurate photometry cannot be performed. .

In view of this, there has been disclosed a photographing apparatus that monitors the light reception signal of the light receiving sensor and controls the strobe so that the preliminary light emission is stopped when the integrated value reaches the light control level (see Patent Document 1). In this case, the light control level is set to a level lower than that at the time of main light emission so that the image sensor is not saturated by strobe light emission.
JP-A-10-170993

  SUMMARY OF THE INVENTION An object of the present invention is to provide a strobe control technique for performing control so that a light receiving sensor is not saturated.

  A strobe device according to an aspect of the present invention includes a strobe unit, a photometric unit having a light receiving sensor that receives reflected light by preliminary light emission and outputs an integrated value of a received light amount in a predetermined integration time, and preliminary light emission by the strobe unit. And a control means for controlling the main light emission after the preliminary light emission based on the photometry result of the photometry means, and the control means is configured to control the focal plane shutter during the main light emission in the flat light emission mode. The integration time of the light receiving sensor is set according to the shutter speed. Note that the integration time of the light receiving sensor may be set based on the set light emission amount of preliminary light emission instead of the shutter speed. The present invention achieves not only a strobe device but also a control method for controlling such a strobe device, a camera or a camera system equipped with the strobe device according to the present invention, and the functions of the above devices. It can also be established as a program.

  According to the present invention, it is possible to perform control so that the light receiving sensor is not saturated.

  Embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of a camera system including a strobe device according to an embodiment of the present invention.

  This camera system includes a camera main body 1, a lens barrel 2 and an external strobe device 3 that are configured separately, and the camera main body 1, the lens barrel 2 and the external strobe device 3 are detachable from each other. It is configured.

  The camera main body 1, the lens barrel 2 and the external strobe device 3 are controlled by a body control microcomputer (hereinafter referred to as Bucom) 150, a lens control microcomputer (hereinafter referred to as Lucom) 250, and a flash control. Each microcomputer (hereinafter referred to as Fucom) 350 executes. In addition, Bucom 150, Lucom 250, and Fucom 350 are electrically connected to each other via communication connectors 251 and 351 when they are combined. In this case, as one camera system, the Lucom 250 and the Fubom 350 operate while being dependent on the Bucom 150 in a dependent manner.

  The lens barrel 2 is configured by holding therein a photographing optical system 201 composed of a plurality of lenses and their driving mechanisms. The photographing optical system 201 is driven by a DC motor (not shown) in the lens driving mechanism 202 and transmits a light beam from the subject, thereby causing an image of the subject formed by the subject light beam to be in a predetermined position (described later). For example, it is constituted by a plurality of optical lenses or the like so as to form an image on the photoelectric conversion surface of the imaging device. The lens barrel 2 is disposed so as to protrude toward the front surface of the camera body 1. The lens barrel 2 is provided with a diaphragm 204 that is driven by a stepping motor (not shown) in the diaphragm driving mechanism 203. Then, the Lucom 250 controls each of these motors in accordance with a command from the Bucom 150.

  The camera body 1 includes various components and the like in each part, and is a photographic optical that is a connecting member for detachably mounting the lens barrel 2 that holds the photographic optical system 201. This is a so-called single-lens reflex camera that is configured with a system mounting portion on the front surface thereof. In addition, the camera body 1 is configured so that a plurality of external strobe devices 3 having different maximum guide numbers can be attached exclusively as required.

  Inside the camera body 1 are various components such as a finder device 101 that constitutes a so-called observation optical system, and a shutter mechanism that controls the irradiation time of the subject luminous flux on the photoelectric conversion surface of the image sensor. The provided shutter unit 102 and the imaging unit 103 for obtaining an image signal corresponding to the subject image are respectively disposed at predetermined positions.

  The viewfinder device 101 receives a reflecting mirror 101a configured to bend the optical axis of a subject light beam that has passed through the photographing optical system 201 and guide it to the observation optical system side, and a light beam emitted from the reflecting mirror 101a. A pentaprism 101b that forms an erect image and an eyepiece 101c that forms an image in an optimal form for magnifying and observing an image formed by the pentaprism 101b are formed.

  The reflecting mirror 101a is configured to be movable between a position retracted from the optical axis of the photographing optical system 201 and a predetermined position on the optical axis. In a normal state, the reflecting mirror 101a is arranged on the optical axis of the photographing optical system 201. They are arranged with a predetermined angle with respect to the optical axis, for example, an angle of 45 degrees.

  Thereby, when the camera system is in the normal state (mirror down), the optical flux of the subject light beam that has passed through the photographing optical system 201 is bent by the reflecting mirror 101a, and the pentagon disposed above the reflecting mirror 101a. The light is reflected toward the prism 101b. On the other hand, while the camera system is performing a photographing operation, the reflecting mirror 101a moves to a predetermined position (mirror up) that is retracted from the optical axis of the photographing optical system 201. Then, it is guided to the imaging unit 103 side.

  As the shutter unit 102, for example, a focal plane type shutter mechanism and its drive circuit, etc., which are generally used in conventional cameras and the like are applied.

  The imaging unit 103 is provided with an imaging element 104 for photoelectric conversion of a subject image that has passed through the photographing optical system 201 as a photoelectric conversion element. The image sensor 104 is protected by a dustproof filter 105 made of a transparent glass member as an optical element disposed between the image sensor 104 and the shutter unit 102. For example, a piezoelectric element 106 is attached to the periphery of the dustproof filter 105 as a part of the vibration means for vibrating the dustproof filter 105 at a predetermined frequency. This piezoelectric element 106 has two electrodes, and this piezoelectric element 106 vibrates the dustproof filter 105 by the dustproof filter drive circuit 107 as a part of the vibration means, and removes dust adhering to the glass surface. It is configured so that it can be removed.

  In the camera body 1, a sub mirror 108, an AF sensor unit 109 for receiving a reflected light beam from the sub mirror 108 and automatically measuring a distance, and an AF sensor driving circuit 110 for driving and controlling the AF sensor unit 109 are provided. A mirror driving mechanism 111 that drives and controls the reflecting mirror 101a, a shutter charge mechanism 112 that charges a spring force for driving the front curtain and rear curtain of the shutter unit 102, and the movement of the front curtain and rear curtain. The shutter control circuit 113, the photometry circuit 114 for measuring light based on the light flux from the pentaprism 101b, and the strobe emission amount at the time of pre-emission are measured by the reflected light from the shutter unit 102 to determine the strobe emission amount at the main emission. A dimming circuit 115 (including a light receiving sensor) is provided.

  Further, in the camera body 1, an LCD monitor 116, an SDRAM 117 provided as a storage area, an image processing controller 120 that performs image processing using a flash ROM 118 and a recording medium 119, and the like are provided. In addition, the electronic recording display function can be provided. As the other storage area, a nonvolatile memory 121 made of, for example, an EEPROM is provided as accessible from the Bucom 150 as a nonvolatile storage means for recording predetermined control parameters necessary for camera control.

  The Bucom 150 is connected with an operation display LCD 151 for notifying the user of the operation state of the camera by display output and a camera operation switch (SW) 152. The camera operation SW 152 is a switch group including operation buttons necessary for operating the camera, such as a release SW, a mode change SW, and a power SW.

  A battery 153 as a power supply and a power supply circuit 154 that converts the voltage of the power supply into a voltage required by each circuit unit constituting the camera system and supplies the power supply circuit 154 are provided in the camera body 1. ing.

  The external strobe device 3 is a light source for photographing a dark subject, and the light emission control circuit 301 controls the light emission amount of the light emitting unit 302. The external strobe device 3 is provided with a strobe capacitor 304 capable of accumulating a predetermined amount of charge under the control of the charge control circuit 303. The light emission control circuit 301 charges and discharges the strobe capacitor 304 to emit light 302. Drive. In addition, the charge control circuit 303 has a voltage detection unit that detects the amount of charge stored in the strobe capacitor 304. The Fucom 350 stores a maximum guide number and a minimum guide number unique to each, and notifies the Bucom 150 of each stored guide number and controls the light emission control circuit 301 and the charge control circuit 303 in accordance with a command from the Bucom 150. To do.

FIG. 2 is a diagram for explaining a light emission state of preliminary light emission and a saturation state due to steady light.
As shown in FIG. 2A, the light emission intensity of the flash rises rapidly after the light emission starts, reaches a maximum value for a predetermined time (for example, 1 millisecond), and then gradually decreases. At this time, the amount of light received by the light receiving sensor (hereinafter referred to as “sensor”) in the light control circuit 115 is integrated (integrated) for a predetermined time (for example, 1 millisecond) as shown in FIG. The integrated value is output from the light receiving sensor.
In this case, for example, considering the case where the stationary light is bright and dark, the output of the light receiving sensor with the stationary light alone is an output as indicated by the luminance B in FIG. 2C when the stationary light is bright. When the stationary light is dark, an output as indicated by the luminance A in FIG. Here, when there is no steady light (that is, only the flash emission amount), an integration curve as shown in FIG. 2D is obtained, but the light quantity due to the steady light shown in FIG. When added to the flash emission amount shown in 2 (d), the curves become as shown in luminance A and luminance B in FIG. 2E, respectively. In the case shown in luminance B, the integrated value is the maximum sensor output. Therefore, the light receiving sensor is saturated.

  The reason why the integrated value at the luminance B exceeds the maximum value of the sensor output is as follows. As in the case of luminance B, when the amount of steady light is large, control is performed to increase the shutter speed so as not to overexpose. Thus, the shutter speed increases as the steady light increases, so the exposure amount can be adjusted by the shutter speed (in addition, the exposure amount can be adjusted by adjusting the aperture, but here only the shutter speed is adjusted. Think). However, since the received light amount is not adjusted for the light receiving sensor as in the image sensor, there is a problem that the integrated value of the received light amount exceeds the maximum value of the sensor output as shown in FIG. Sometimes. This problem is likely to occur in a bright environment such as daytime synchro or indoor strobe photography.

  In such an environment, when the shutter speed becomes high, and the shutter speed becomes high, as shown in FIG. 3, the shutter is not fully opened, and the slit portion constituted by the front curtain and the rear curtain Control is performed such that light passes only through the slit and exposure is performed while scanning the surface of the image sensor while the slit moves. Therefore, in such a case, control called flat light emission (mode) is performed so that the amount of light reaches the surface of all the imaging elements under the same conditions. This flat light emission is a light emission method in which the flash light emission amount is controlled uniformly (constant in time) while the shutter is driven. As described above, under steady light where the sensor output is saturated, the shutter speed is also increased. Therefore, in one embodiment of the present invention, particularly when such high-speed shutter control is performed. set to target.

Here, when comparing the guide number (hereinafter referred to as “Gv”) at the time of flash light emission and flat light emission, which are normal light emission modes, as shown in FIG. 4, the maximum guide number (hereinafter referred to as “maximum Gv”) is obtained. Is the largest during flash emission, and becomes smaller as the shutter speed increases during flat emission. This is because when the shutter speed is increased, the width of the slit is reduced, so that the amount of light received by the pixels on the image sensor relatively decreases even if the amount of light emitted from the strobe is constant. Further, the minimum guide number (hereinafter referred to as “minimum Gv”) becomes smaller as the shutter speed becomes faster during flat light emission. In this case, the number of times of preliminary light emission and the guide number of preliminary light emission at the time of flat light emission are obtained by the following equations.
Number of preliminary flashes = (maximum Gv-minimum Gv + AUTOISO sensitivity increase amount + coefficient)
/ Sensor dynamic range
Preliminary light emission Gv = minimum Gv + log ₂ {(imaging element output × sensor sensitivity)
/ (Image sensor sensitivity x Target sensor output target value)}
In the above formula, the coefficient is a coefficient for adjusting the variation between individuals, and is preferably 1.0. Also, the AUTOISO sensitivity increase amount is 2.0 when the ISO 100 is increased from ISO 100 to ISO 400, for example.

  Further, the reason why the amount of preliminary light emission can be reduced in the case of flat light emission will be described with reference to FIG. FIG. 5 is a diagram showing the relationship between the subject distance and the photometric value of the reflected light at the time of preliminary light emission (flash light emission) set according to the set shutter speed when main light emission is in flat mode light emission. When the sensor output is defined as 0 to 100%, the range (dynamic range) normally used for detection is about 10% to 80% in consideration of the linearity of the sensor output. About 60% is set as the target value (that is, the upper limit) of the closest sensor output. In this case, when the relationship between the subject distance and the sensor output when the shutter speed is 1/1000, 1/2000, and 1/4000, the minimum and maximum guide numbers decrease as the shutter speed increases. The possible range is also reduced. Therefore, the faster the shutter speed, the smaller the amount of preliminary light emission.

Therefore, in one embodiment of the present invention, the integration time of the amount of light received by the sensor during preliminary light emission (hereinafter simply referred to as “integration time”) is determined according to the shutter speed. In other words, for example, as shown in FIG. 6, when the shutter speed is 1/1000, the light emission amount is such that the light emission is stopped in 0.8 milliseconds after the start of the preliminary light emission (this light emission start). For example, the integration time is set to (0.8 + 0.2) = 1 millisecond. Here, 0.2 milliseconds is a margin value. In this case, the preliminary light emission time is shortened as the shutter speed increases. For example, in the case of a shutter speed of 1/2000, the light emission time is 0.5 milliseconds, and in the case of a shutter speed of 1/4000. The light emission time is set to 0.3 milliseconds, and the integration time is accordingly set to O. By setting the time to 7 milliseconds and 0.5 milliseconds, saturation of the integrated value of the sensor can be prevented with respect to the incidence of strong steady light.
The operation control method controlled by the Bucom 150 in the embodiment of the present invention as described above will be described with reference to the flowcharts of FIGS.
First, an exposure condition is set based on a photometric result obtained by the photometric element (step A1). In this case, for example, shutter speed, aperture value, ISO sensitivity, and the like are set as the exposure conditions. Here, it is determined from the shutter speed whether the flash emission mode is the flat emission mode (step A2). Here, if the light emission mode is not the flat light emission mode, the integration time is set to a predetermined time (default time according to the flash light emission mode: for example, 1 millisecond), and the process is terminated. In step A2, if the light emission mode is the flat light emission mode, the integration time of the sensor at the time of preliminary light emission is calculated by an operation based on the flowchart shown in FIG. 9 described later (step A3).

  Next, with reference to FIG. 9, the details of the operation for obtaining the integration time of the sensor during preliminary light emission by calculation will be described. A preliminary light emission guide number is calculated based on the exposure conditions set in step A1 of FIG. 8 (step B1), and a charging voltage during light emission is detected (step B2). Next, based on the preliminary light emission guide number and the charging voltage, the light emission time is determined based on the table shown in FIG. 7 (step B3). In step B3, linear interpolation is performed between the voltages, and when the charging voltage is smaller than 280 V, extrapolation is performed linearly. And then. The integration time of the sensor is calculated from the flash light emission time (that is, the preliminary light emission amount) set according to the exposure conditions including the shutter speed (step B4). In the above description, the sensor integration time is described as providing a predetermined margin time (for example, 0.2 milliseconds) in the light emission time, but the light emission time is multiplied by a predetermined coefficient (for example, 1.2 times). ) May be used as the integration time.

FIG. 10 is a flowchart showing another operation related to the integration time calculation of the preliminary light emission sensor.
In this case, as in the case of FIG. 9, a preliminary light emission guide number for setting the light emission amount of the preliminary light emission is calculated (step C1). In this operation, in order to simply obtain the integration time, instead of the preliminary light emission guide number, for example, the following equation:
Integration time = constant x shutter speed
Is used to set the integration time (step C2). The integration time may be set by using a table showing the relationship between the flash emission amount and the emission time at each voltage before emission as shown in FIG.

  As described above, the sensor integration time is set short during preliminary light emission at a high shutter speed. Further, during preliminary light emission at a high shutter speed, the integration time is set shorter as the preliminary light emission amount becomes smaller. By performing such control, saturation of the light receiving sensor can be prevented.

The present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention at the stage of implementation.
For example, in the above-described embodiment, an embodiment in which the present invention is applied to a system including an external strobe device and a camera main body is shown, but the present invention is naturally applicable to a camera having a built-in strobe. Moreover, as a camera, it is applicable also to the camera apparatus mounted, for example in a mobile telephone, PDA, etc.
In the above embodiment, the dimming circuit 115 is provided in the camera body 1, but may be provided in the external strobe device 3.
Further, the above embodiments include inventions at various stages, and various inventions can be extracted by appropriately combining a plurality of disclosed constituent elements.

  In addition, for example, even if some structural requirements are deleted from all the structural requirements shown in each embodiment, the problem described in the column of the problem to be solved by the invention can be solved, and the effect described in the effect of the invention Can be obtained as an invention.

1 is a diagram showing a schematic configuration of a camera system including a strobe device according to an embodiment of the present invention. The figure for demonstrating the light emission state of preliminary light emission, and the saturation condition by stationary light. The figure which shows the operation | movement at the time of the high-speed shutter of a focal plane shutter. The figure which shows the guide number in each shutter speed at the time of flash emission, and the shutter number at the time of flat light emission. The figure for demonstrating the reason for the amount of light emission of preliminary light emission being small in the case of flat light emission. The figure which shows the relationship between the light emission time according to shutter speed, and the integration time set corresponding to the light emission time. The table which shows the relationship between the flash light emission amount and light emission time in each voltage before light emission. The flowchart which shows the operation | movement concerning one Embodiment of this invention. The flowchart which shows the operation | movement concerning one Embodiment of this invention. The flowchart which shows the other operation | movement which concerns on the integral time calculation of a preliminary light emission sensor.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Camera body part, 2 ... Lens barrel, 3 ... External strobe device, 45 ... Angle, 101 ... Finder apparatus, 101a ... Reflector, 101b ... Pentaprism, 101c ... Eyepiece, 102 ... Shutter part, 103 ... Imaging Unit: 104 ... Image sensor, 105 ... Dustproof filter, 106 ... Piezoelectric element, 107 ... Dustproof filter drive circuit, 108 ... Sub mirror, 109 ... AF sensor unit, 110 ... AF sensor drive circuit, 111 ... Mirror drive mechanism, 112 ... Shutter Charging mechanism, 113 ... shutter control circuit, 114 ... photometry circuit, 115 ... dimming circuit, 116 ... liquid crystal monitor, 117 ... SDRAM, 118 ... ROM, 119 ... recording medium, 120 ... image processing controller, 121 ... non-volatile memory, 150: microcomputer for body control, 151: operation Display LCD, 152 ... Camera operation switch, 153 ... Battery, 154 ... Power supply circuit, 201 ... Shooting optical system, 202 ... Lens drive mechanism, 203 ... Aperture drive mechanism, 250 ... Microcomputer for lens control, 251.351 ... Communication Connector, 301... Light emission control circuit, 302... Light emission unit, 303... Charge control circuit, 304.

Claims (5)

Strobe means,
Photometric means having a light receiving sensor that receives reflected light by preliminary light emission and outputs an integrated value of the amount of light received in a predetermined integration time;
Controlling the preliminary light emission and photometry means by the strobe means, and a control means for controlling the main light emission after the preliminary light emission based on the photometric result of the photometry means,
The strobe device characterized in that the control means sets the integration time of the light receiving sensor in accordance with the shutter speed of the focal plane shutter during main light emission in the flat light emission mode. Strobe means,
Photometric means having a sensor that receives reflected light by preliminary light emission and outputs an integrated value of the amount of light received in a predetermined integration time;
Controlling the preliminary light emission and photometry means by the strobe means, and a control means for controlling the main light emission after the preliminary light emission based on the result of the photometry means,
The strobe device, wherein the control means sets an integration time of the sensor in accordance with a light emission amount of preliminary light emission. 3. The strobe device according to claim 2, wherein the control means sets the integration time of the sensor in accordance with the shutter speed of the focal plane shutter during main light emission in the flat light emission mode. In a control method of a strobe device having a strobe means and a photometry means for measuring reflected light by preliminary light emission, and controlling the preliminary light emission by the strobe light means, the main light emission in the flat light emission mode after the photometry means and preliminary light emission,
A control method for a strobe device, characterized in that, during main light emission, a light emission amount of preliminary light emission is set and an integration time of the sensor is set according to the light emission amount of preliminary light emission. In cameras with built-in strobe devices or detachable strobe devices,
Photometric means having a light receiving sensor that receives reflected light by preliminary light emission and outputs an integrated value of the amount of light received in a predetermined integration time; controls preliminary light emission and photometric means by the strobe device; and photometric results of the photometric means Control means for controlling the main light emission after the preliminary light emission based on
In the flat light emission mode, the control means sets the integration time of the light receiving sensor in accordance with the shutter speed of the focal plane shutter during main light emission.

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