JP2006243372A - Camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten a diaphragm switching time without lowering the aperture accuracy and the exposure accuracy of a camera. <P>SOLUTION: The actual diaphragm value of a diaphragm to the same target diaphragm value is different according as an opening or closing direction of a driving direction by a diaphragm driving mechanism. The actual diaphragm value to the target diaphragm value is obtained and stored in a flush memory. When a shutter button is half-depressed when photographing, AE processing and AF processing are started. In the AE processing, the diaphragm driving mechanism is driven and the diaphragm is set to the target diaphragm value corresponding to the luminance integrated value of an imaging signal. The actual diaphragm value corresponding to the target diaphragm value is read out from the flush memory according as the opening α or closing β direction of the driving direction of the diaphragm driving mechanism, and shutter speed is calculated based on the actual diaphragm value. When the shutter button is fully depressed, the imaging signal is read out from a CCD during charge storage time corresponding to the shutter speed. The imaging signal is converted into image data and stored in a memory card through various kinds of processing. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a camera having hysteresis in an aperture diameter of a diaphragm depending on a driving direction or a driving speed.

  An iris diaphragm is generally used for the diaphragm of the camera. Many iris diaphragms have hysteresis due to a mechanical cause when the aperture is closed from the wide aperture side to the small aperture side and when the iris aperture is opened from the small aperture side to the wide aperture side. If there is such a hysteresis, there is a difference between the target aperture value (target aperture value) and the actual aperture value (actual aperture value), so that it is not possible to perform photographing with appropriate exposure.

  In order to eliminate such hysteresis, a method of stopping the diaphragm from one direction is generally used. For this reason, when the aperture diameter in the opposite direction is necessary, the aperture driving mechanism is controlled so that the aperture blade is overrun once and then reversed to stop at the desired aperture diameter position. In addition, there are diaphragms having hysteresis depending on whether the driving speed is low or high. In such a diaphragm, in general, the diaphragm is always driven at a low speed.

In such an aperture driving method, since it takes time to set the aperture, a shutter time lag from when the shutter button is pressed down until an image is actually recorded becomes longer. As an invention for improving this, for example, Patent Document 1 is known. Japanese Patent Application Laid-Open No. 2004-228561 proposes reducing the number of aperture value changes by performing photometry before shifting to autofocus (AF) control to determine the aperture value during shooting.
JP 2004-64279 A

  However, in Patent Document 1, it is assumed that the aperture is determined by a single metering without changing the aperture at the time of metering. When the aperture must be changed and metering must be performed again, the shutter time lag is short. There is a problem of not becoming.

  It is an object of the present invention to provide a camera that can shorten the aperture switching time without reducing the aperture accuracy and the exposure accuracy.

  The camera of the present invention includes a photometric means for measuring subject brightness, an aperture value selecting means for selecting one target aperture value from a plurality of target aperture values based on a photometric value obtained by the photometric means, and a selected target aperture In a camera equipped with a diaphragm drive mechanism that drives the diaphragm based on the value, each of the case where the diaphragm is driven in the closing direction from the open diaphragm toward the minimum diaphragm and the case where the diaphragm is driven in the opening direction from the minimum diaphragm to the open diaphragm For each of the target aperture values, a subject having a constant brightness is photographed, the amount of light passing through the aperture is measured, and the actual aperture values in the closing direction and the open direction for each target aperture value are calculated from the measurement results, and the storage unit The aperture value selection means selects a target aperture value based on a photometric value at the time of shooting, and depending on whether the driving direction of the aperture is a closing direction or an opening direction, Read an actual aperture value corresponding to the target aperture value from the storage unit, and performs calculation of the shutter speed based on the actual aperture.

  Further, a photometric means for measuring subject brightness, an aperture value selecting means for selecting one target aperture value from a plurality of target aperture values based on a photometric value obtained by the photometric means, and based on the selected target aperture value In a camera provided with an aperture drive mechanism for driving an aperture, the target for each of the case where the aperture is driven in the closing direction from the open aperture toward the minimum aperture and the aperture in the open direction from the minimum aperture toward the open aperture Photographing a subject with a constant brightness for each aperture value, measuring the amount of light passing through the aperture, calculating the actual aperture value in the closing direction and the open direction for each target aperture value, and calculating each actual aperture value. Each stop position of the motor that drives the diaphragm mechanism is obtained for each of the closing direction and the opening direction so that the values match the corresponding target aperture values, and the motor is stopped at each stop position. The motor stop position data to be stored is stored in the storage unit, and at the time of shooting, the aperture value selection means selects the target aperture value based on the photometric value, and the driving direction of the aperture is either the closing direction or the opening direction. Depending on whether there is, the motor stop position data corresponding to the target aperture value is read from the storage unit, and the motor is stopped.

  Further, a photometric means for measuring subject brightness, an aperture value selecting means for selecting one target aperture value from a plurality of target aperture values based on a photometric value obtained by the photometric means, and based on the selected target aperture value In a camera having an aperture drive mechanism for driving an aperture, the aperture drive mechanism is configured such that a difference between a target aperture value selected by the aperture value selection unit and a current aperture value of the aperture is larger than a predetermined threshold value. The aperture is driven at a high speed that is faster than the normal low speed, and the actual aperture value differs between when the aperture is driven at the low speed and when driven at the high speed, and the target aperture value is Each time the aperture is driven at a low speed and set to a target aperture value, and when it is driven and set at a high speed, an object with a constant brightness is photographed and the amount of light passing through the aperture is measured. Each target aperture value from the measurement results The actual aperture value at the time of low speed driving and high speed driving at this time is calculated and stored in the storage unit, and at the time of photographing, the aperture value selection means selects the target aperture value based on the photometric value, and The actual aperture value corresponding to the target aperture value is read from the storage unit depending on whether the aperture driving speed is low speed or high speed, and the shutter speed is calculated based on the actual aperture value. To do.

  According to the camera of the present invention, the actual aperture value in the closing direction and the open direction at each target aperture value is calculated and stored in the storage unit, and at the time of shooting, the target aperture value is selected based on the photometric value, The actual aperture value corresponding to the target aperture value is read from the storage unit according to the drive direction of the aperture, and the shutter speed is calculated based on this actual aperture value, thus shortening the aperture switching time without reducing aperture accuracy or exposure accuracy it can.

  Further, the stop positions of the motors in the closing direction and the opening direction are obtained so that the actual aperture values in the closing direction and the opening direction respectively match the corresponding target aperture values, and the motor stop position data is stored in the storage unit. When photographing, the target aperture value is selected based on the photometric value, and motor stop position data corresponding to the target aperture value is read from the storage unit depending on whether the aperture driving direction is the closing direction or the opening direction. Since the motor is stopped, the aperture switching time can be shortened without reducing the aperture accuracy and exposure accuracy.

  In addition, the light intensity is measured for each target aperture value when the aperture is driven and set at a low speed and when the aperture is driven and set at a high speed. Each actual aperture value is calculated and stored in the storage unit. At the time of shooting, the target aperture value is selected based on the photometric value, and the target aperture value is determined depending on whether the aperture drive speed is low or high. Since the corresponding actual aperture value is read from the storage unit and the shutter speed is calculated based on the actual aperture value, the aperture switching time can be shortened without reducing the aperture accuracy or the exposure accuracy.

  In FIG. 1 illustrating the configuration of the digital camera 10 according to the first embodiment of the present invention, the CPU 11 performs the operation of the digital camera 10 via the I / O bus 13 according to various operation signals input from the operation unit 12. Control each part of the main body. The operation unit 12 includes a power button 14, a mode selection dial 15, a zoom button 16, a shutter button 17, and the like. The mode selection dial 15 can alternatively select a shooting mode or a playback mode in which a shot image is played back and displayed on a liquid crystal display (LCD) 18.

  The zoom lens 21 as a photographing lens includes a lens 22 and a diaphragm 23. The lens 22 includes a front group lens that is a variator lens and a rear group lens that is a compensator lens having a focusing function. The lens 22 is driven by a lens driving mechanism 25 including a stepping motor to change the optical zoom magnification and adjust the focus.

  The aperture 23 is step-driven by an aperture drive mechanism 26 including a stepping motor, and the aperture diameter is switched to one of a plurality of target aperture values. For example, when the open aperture of the aperture 23 is F2.8 and the minimum aperture is F11, the target aperture value is F4, F5.6, and F8 including the open aperture F2.8 and the minimum aperture F11. The lens driving mechanism 25 and the aperture driving mechanism 26 are driven by motor drivers 27 and 28 controlled by the CPU 11.

  Behind the zoom lens 21, a CCD 30 is disposed as a solid-state imaging device. The CCD 30 is connected to the CPU 11 via a timing generator (TG) 31. In the shooting mode, the CPU 11 controls the TG 31 to generate a timing signal (clock pulse), and the CCD 30 is driven by the timing signal input from the TG 31.

  An optical image formed by the zoom lens 21 is formed on the light receiving surface of the CCD 30 and is photoelectrically converted to output an analog imaging signal. This image pickup signal is input to a correlated double sampling circuit (CDS) 32 and output as R, G, and B image data corresponding to the amount of charge accumulated in each cell of the CCD 30. The image data output from the CDS 32 is amplified by an amplifier (AMP) 33 and converted from an analog signal to digital image data by an A / D converter (A / D) 34.

  The image input controller 36 is connected to the CPU 11 via the I / O bus 13. Further, an internal memory 38 is connected to the I / O bus 13. As the internal memory 38, for example, an SDRAM (Synchronous Dynamic Random Access Memory) is used. The CPU 11 controls the image input controller 36 to store the image data output from the A / D 34 in the internal memory 38. The image signal processing circuit 41 accesses the image data stored in the internal memory 38 and performs various image processing such as gradation conversion, white balance correction, and γ correction processing.

  In the shooting mode, the CCD 30 performs an imaging process at a predetermined frame rate, the image processing is performed on the acquired image data, and the processed captured image is displayed on the LCD panel 18 as a live image. The LCD panel 18 is driven by the LCD driver 43. The LCD driver 43 includes an image memory and a D / A converter. The processed image data temporarily stored in the image memory is converted into, for example, an NTSC analog signal by the D / A converter. The data is output to the LCD panel 18.

  When the release operation is performed, the CCD 30 acquires main image data having a larger number of pixels than the live image for through display. The main image data is subjected to the above-described image processing and is subjected to compression processing by a compression / decompression processing circuit 44 in a predetermined compression format (for example, JPEG format). The main image data subjected to the compression processing is stored in the memory card 46 via the media controller 45.

  In addition to the media controller 45 and the like, an AE detection circuit 48, an AF detection circuit 49, and a flash memory 50 are connected to the I / O bus 13. The AF detection circuit 49 decomposes the imaging signal into spatial frequency components, and sends the high frequency component contrast data to the CPU 11. The CPU 11 controls the lens driving mechanism 25 via the motor driver 27 to move the focusing lens forward and backward in the optical axis direction and stop it at a position where the contrast of the high frequency component of the subject image is highest.

  The AE detection circuit 48 integrates the luminance signal of the image pickup signal, and sends the integrated luminance value (subject luminance value) as the obtained photometric data to the CPU 11. The CPU 11 selects a target aperture value corresponding to the subject brightness value from a plurality of predetermined target aperture values, and sets the shutter speed corresponding to the target aperture value according to the program line of the shooting mode. Further, the CPU 11 outputs an aperture control signal to the aperture drive mechanism 26 via the motor driver 28 so that the target aperture value is set to the aperture 23. The aperture drive mechanism 26 opens and closes the aperture 23 according to the aperture control signal.

  As shown in FIG. 2, the aperture 23 is driven by the aperture drive mechanism 26 depending on whether the direction is an open direction α (minimum aperture → open aperture) or a close direction β (open aperture → minimum aperture). The aperture diameter (actual aperture value) actually set for the same target aperture value M is different (A or B) and has a so-called hysteresis.

  Therefore, in the present embodiment, the actual aperture values A and B for the target aperture value M are obtained for each of the opening direction α and the closing direction β and stored in the flash memory 50 when the digital camera 10 is manufactured. . In addition, the code | symbol m1 in a figure is the mechanical stop position of the aperture drive mechanism 26 corresponding to the target aperture value M, more specifically, for example, the stop position of the motor.

  The flash memory 50 is a well-known non-volatile memory, and stores various programs and data, various control parameters, and the like in addition to the actual aperture value for each target aperture value.

  In order to obtain the actual aperture value A, first, the aperture 23 is set to the minimum aperture, and the CPU 11 sends a command for setting the aperture 23 to the target aperture value M to the motor driver 28. Thereby, after the aperture driving mechanism 26 drives the aperture 23 in the opening direction α, the motor of the aperture driving mechanism 26 is stopped at the stop position m1. In this state, the test pattern illuminated with a constant luminance is photographed by the digital camera 10. The subject brightness value output from the AE detection circuit 48 is input to the CPU 11, and the aperture value corresponding to the subject brightness value is obtained according to the program line of the shooting mode. This becomes the actual aperture value A in the opening direction α with respect to the target aperture value M.

  In order to obtain the actual aperture value B, first, the aperture 23 is set to the full aperture, and the CPU 11 sends a command for setting the aperture 23 to the target aperture value M to the motor driver 28. Thereby, after the aperture drive mechanism 26 drives the aperture 23 in the closing direction β, the motor of the aperture drive mechanism 26 is stopped at the stop position m1. In this state, the test pattern illuminated with a constant luminance is photographed by the digital camera 10. The subject brightness value output from the AE detection circuit 48 is input to the CPU 11, and the aperture value corresponding to the subject brightness value is obtained according to the program line of the shooting mode. This becomes the actual aperture value B in the closing direction β with respect to the target aperture value M.

  In this way, the actual aperture values A and B are obtained for each of a plurality of target aperture values, for example, F2.8, F4, F5.6, F8, and F11, and stored in the flash memory 50.

  To shoot with the digital camera 10 configured as described above, as shown in FIG. 3, when the power button 14 is pressed (st1) and the mode selection dial 15 is operated to select the shooting mode (st2), the image is displayed. The image data output from the input controller 36 is displayed on the LCD 18 as a through image via the LCD driver 43 (st3). Using the LCD 18 as an electronic viewfinder, the display image on the LCD 18 is observed to perform framing. When the user wants to take a picture, first, when the shutter button 17 is half-pressed (lightly touching the shutter button) (st4), the AE process (st5) and the AF process (st6) are started.

  As shown in FIG. 4, in the AE process, the AE detection circuit 48 takes in the luminance signal of the imaging signal and performs an integration operation (st10), and sends this luminance integration value to the CPU 11. The CPU 11 drives the aperture driving mechanism 26 to set the aperture 23 to the target aperture value corresponding to the subject luminance value according to the program line of the shooting mode, and sets the aperture 23 to the target aperture value (st11). The CPU 11 monitors the drive direction of the aperture drive mechanism 26, and reads out the actual aperture value corresponding to the target aperture value from the flash memory 50 depending on whether the opening direction α or the closed direction β (st12). Based on the above, the shutter speed is calculated (st13).

  In the AF process, the AF detection circuit 49 decomposes the imaging signal into spatial frequency components, and sends contrast data of high frequency components to the CPU 11. The CPU 11 controls the lens driving mechanism 25 via the motor driver 27 using, for example, a range from 1 mm to infinity (∞) as an autofocus search range, and advances and retracts the rear group lens of the lens 22 in the optical axis direction. The position where the contrast of the high frequency component of the subject image is highest is found and stopped.

  If the image displayed on the LCD 18 is acceptable, the user presses the shutter button 17 deeper as it is (st7). At the next moment, the image pickup signal is read out from the CCD 30 during the charge accumulation time corresponding to the shutter speed. The imaging signal output from the CCD 30 is input to the image input controller 36 via the CDS 32, the AMP 33 and the A / D converter 34. The image data output from the image input controller 36 is compressed by the compression / decompression processing circuit 44 to reduce the data capacity, and then stored in the memory card 46 via the media controller 45 (st8).

  Next, a second embodiment of the present invention will be described with reference to FIG. In each embodiment described below, the mechanical and electrical configuration of the digital camera is the same as that of the first embodiment, and thus the description thereof is omitted. In the second embodiment of the present invention, the same actual aperture value, that is, the target aperture value M and the actual aperture value are the same regardless of the drive direction regardless of whether the drive direction of the aperture drive mechanism 26 is the open direction α or the close direction β. The stop positions m2 and m3 of the motor of the aperture driving mechanism 26 with respect to the target aperture value M in the opening direction α and the closing direction β are obtained, and the motor stop position data is stored in the flash memory 50.

  In order to obtain the motor stop position m2, first, as in the first embodiment, the actual aperture value A in the opening direction α is obtained (see FIG. 2). Then, based on the difference between the target aperture value M and the actual aperture value A, it is determined how much the motor is driven from the stop position m1 to shift the stop position so that the actual aperture value matches the target aperture value M. Calculate and determine a new stop position m2. When determining the stop position m2, there is an error inherent to the diaphragm drive mechanism 26, so it is preferable to confirm by an experiment. The method for obtaining the stop position m3 of the motor is the same as that for the stop position m2 except that the driving direction of the diaphragm drive mechanism 26 (the rotational drive direction of the motor) is different.

  In this manner, the motor stop positions m2 and m3 are obtained for each of a plurality of target aperture values, for example, F2.8, F4, F5.6, F8, and F11, and stored in the flash memory 50. At the time of actual photographing, the CPU 11 reads the corresponding motor stop position data from the flash memory 50 depending on whether the driving direction of the aperture driving mechanism 26 is the opening direction α or the closing direction β, thereby controlling the aperture driving mechanism 26.

  Next, a third embodiment of the present invention will be described with reference to FIG. In the third embodiment, for example, when the diaphragm drive mechanism 26 moves the diaphragm 23 greatly from the open diaphragm F2.8 to the minimum diaphragm F11, the diaphragm drive mechanism 26 operates at a high speed, and when the diaphragm drive mechanism 26 performs a small movement of about one stage (1 EV). Drives the diaphragm 23 at a low speed, and has two actual diaphragm values C and D for the motor stop position m4 of the same diaphragm driving mechanism 26.

  For each target aperture value, the actual aperture value when the aperture drive mechanism 26 is driven at high speed and low speed is measured, and each actual aperture value is stored in the flash memory 50. At the time of shooting, the corresponding actual aperture value is read from the flash memory 50 according to the driving speed of the aperture driving mechanism 26, and the shutter speed is calculated thereby.

  In the first embodiment described above, photometry is performed by half-pressing the shutter button, the actual aperture value corresponding to the target aperture value is read from the flash memory according to the driving direction of the aperture drive mechanism, the shutter speed is calculated, and the shutter button is pressed. When the shutter button is fully pressed, the image is recorded as it is with the aperture and shutter speed determined when the shutter button is pressed halfway. However, the subject brightness may change significantly when the shutter button is shifted from halfway to fully pressed. obtain.

  Therefore, it is preferable to perform photometry (main photometry) again when the shutter button is fully pressed (during shooting). In this case, the driving direction of the aperture driving mechanism may be changed from the opening direction α to the closing direction β, for example. In this case, the aperture diameter (actual aperture value) is shifted with respect to the same target aperture value. Therefore, when the target aperture value is not changed in this photometry and the driving direction of the aperture driving mechanism is changed, the shutter speed is corrected based on the driving direction of the aperture driving mechanism without reading the actual aperture value again. . This correction data is stored in advance in a flash memory.

  Instead of correcting the shutter speed, the ISO sensitivity may be corrected (AMP gain is corrected). ISO sensitivity correction data based on the driving direction of the aperture driving mechanism is stored in advance in a flash memory.

  The embodiment described above is a digital camera, but the present invention is not limited to this, and may be a silver salt camera using a photographic film.

It is a block diagram which shows the schematic structure of the digital camera of this invention. It is a graph which shows the relationship between the actual aperture diameter of 1st Embodiment, and the stop position of the motor of an aperture drive mechanism. It is a flowchart which shows the main sequences of 1st Embodiment. It is a flowchart which shows the main sequences of the AE process of 1st Embodiment. It is a graph which shows the relationship between the actual aperture diameter of 2nd Embodiment, and the stop position of the motor of an aperture drive mechanism. It is a graph which shows the relationship between the actual aperture diameter of 3rd Embodiment, and the stop position of the motor of an aperture drive mechanism.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Digital camera 23 Aperture 26 Aperture drive mechanism 48 AE detection circuit 50 Flash memory

Claims (3)

Metering means for metering subject brightness, aperture value selection means for selecting one target aperture value from a plurality of target aperture values based on the photometric value obtained by the photometry means, and aperture setting based on the selected target aperture value In a camera equipped with an aperture drive mechanism for driving,
For each of the cases where the aperture is driven in the closing direction from the open aperture toward the minimum aperture and the aperture is driven in the open direction from the minimum aperture toward the open aperture, a subject with a constant brightness is photographed for each target aperture value. The amount of light passing through is measured, and the actual aperture value in the closing direction and the opening direction at each target aperture value is calculated from the measurement result and stored in the storage unit.
At the time of shooting, the aperture value selection unit selects a target aperture value based on a photometric value, and an actual aperture value corresponding to the target aperture value depending on whether the driving direction of the aperture is a closing direction or an opening direction Is read out from the storage unit, and the shutter speed is calculated based on the actual aperture value. Metering means for metering subject brightness, aperture value selection means for selecting one target aperture value from a plurality of target aperture values based on the photometric value obtained by the photometry means, and aperture setting based on the selected target aperture value In a camera equipped with an aperture drive mechanism for driving,
For each of the cases where the aperture is driven in the closing direction from the open aperture toward the minimum aperture and the aperture is driven in the open direction from the minimum aperture toward the open aperture, a subject with a constant brightness is photographed for each target aperture value. The amount of light passing through is measured, and the actual aperture value in the closing direction and the open direction at each target aperture value is calculated from the measurement result, and the actual aperture value matches the corresponding target aperture value, respectively. Each stop position of the motor that drives the diaphragm mechanism in each of the closing direction and the opening direction is obtained, and motor stop position data for stopping the motor at each stop position is stored in the storage unit,
At the time of shooting, the aperture value selection unit selects a target aperture value based on a photometric value, and the motor stop position corresponding to the target aperture value depends on whether the driving direction of the aperture is a closing direction or an opening direction. A camera that reads data from a storage unit and stops a motor. Metering means for metering subject brightness, aperture value selection means for selecting one target aperture value from a plurality of target aperture values based on the photometric value obtained by the photometry means, and aperture setting based on the selected target aperture value In a camera equipped with an aperture drive mechanism for driving,
When the difference between the target aperture value selected by the aperture value selection unit and the aperture value of the current aperture is larger than a predetermined threshold, the aperture drive mechanism stops the aperture at a higher speed than the normal low speed. Drive the
The aperture is different from the actual aperture value when driven at the low speed and when driven at the high speed,
For each of the target aperture values, the amount of light passing through the aperture is determined by shooting a subject with a constant brightness when the aperture is driven at a low speed and set to the target aperture value and when driven at a high speed and set. Measure, and calculate the actual aperture value at the time of low speed driving and high speed driving at each target aperture value, and store it in the storage unit.
At the time of shooting, the aperture value selection unit selects a target aperture value based on a photometric value, and an actual aperture value corresponding to the target aperture value depending on whether the aperture driving speed is low speed or high speed Is read out from the storage unit, and the shutter speed is calculated based on the actual aperture value.

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