JP3713139B2 - Single-lens reflex camera - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a single-lens reflex camera in which a reflex mirror that moves between a finder observation position and a photographing position is driven by a motor.
[0002]
[Prior art]
In a single-lens reflex camera of a type in which a reflex mirror (hereinafter simply referred to as a mirror) is moved between a finder observation position and a photographing position, the mirror is moved to a photographing position immediately before exposure is performed. There are various known mirror movement mechanisms, such as those that use a spring force to flip the mirror, those that use a magnet, and those that use a motor. In any case, the mirror moves rapidly just before exposure. This is likely to cause camera shake because vibration is likely to occur.
[0003]
It is also known to use a shock absorber such as an air damper or an oil damper in order to suppress vibration when the mirror is moved, but there are disadvantages in terms of cost and installation space. In this regard, in the case where the mirror is moved by the motor, the generation of vibration can be reduced by controlling the driving speed of the motor during the movement of the mirror.
[0004]
Moving the mirror by driving the motor is particularly effective in a large format type single-lens reflex camera using a Brownie film. In a large format camera, the size of the mirror is increased, and when a lens shutter is used, a movable light shielding plate is provided in front of the film. This light shielding plate needs to be moved immediately before exposure. Therefore, in order to move the large mirror and the light shielding plate without vibration, it is advantageous to operate them by driving a common motor.
[0005]
In the camera described in Japanese Patent Publication No. 7-60243, when the moving mechanism of the mirror and the light shielding plate is operated by driving the motor, not only the movement mechanism itself is devised to reduce the vibration of the mirror or the light shielding plate itself, but also the motor. In order to suppress vibration at startup, the drive voltage supplied to the motor is gradually increased so that the drive speed does not change abruptly. In order to gradually increase the driving speed of the motor, it is sufficient to gradually increase the voltage level of the driving voltage as described in the above publication. However, since the voltage level that is an analog amount is changed almost continuously, the circuit There is a difficulty that the configuration is easily complicated, and that it is easily affected by fluctuations in power supply voltage and noise.
[0006]
Under these circumstances, an ordinary DC motor is used for driving a mirror, and an attempt is made to add pulse width modulation (PWM) to the drive voltage supplied to the DC motor in order to control the drive speed. Yes. In the motor drive method using pulse width modulation, when a pulse voltage of a constant voltage level is supplied to a DC motor and driven at a constant frequency, the pulse width of the pulse voltage is controlled according to the target motor drive speed. . When the motor is started, a pulse voltage having a narrow pulse width is supplied, and a pulse voltage having a wide pulse width is gradually supplied, so that the motor can be started slowly.
[0007]
In order to change the pulse width of the pulse voltage, it is possible to use a microcomputer for sequence control built in the camera. In other words, since the microcomputer is supplied with clock pulses whose frequency is significantly higher than the frequency of the pulse voltage, the pulse width of the pulse voltage can be varied based on the number of clock pulses. This makes it possible to control the motor driving speed digitally without changing the driving voltage supplied to the motor and digitally changing the driving speed of the motor. A highly efficient mirror driving mechanism can be obtained.
[0008]
[Problems to be solved by the invention]
However, for example, when the power supply battery of the camera is exhausted or the ambient temperature is remarkably lowered, the voltage level of the pulse voltage is lowered accordingly, and the driving speed of the motor is reduced. Accordingly, the time required for the mirror to retract from the viewfinder observation position to the photographing position becomes long, and the time lag from when the shutter release operation is performed to when the exposure is performed becomes large, causing the photographer to feel uncomfortable.
[0009]
In addition, various interchangeable lenses having different focal lengths are usually prepared for a single-lens reflex camera. Among them, a telephoto lens has a long lens barrel length and a heavy weight with a focal length. Therefore, when the telephoto lens is used, slight vibration caused by driving the motor is increased on the lens side, and camera shake is likely to occur.
[0010]
Furthermore, in a camera having a tilt function, the photographing lens can be shifted or tilted in various directions. However, when such a tilt function is used, the overall weight balance becomes unstable. Therefore, slight vibration due to driving of the motor is likely to cause a large amount of camera shake.
[0011]
The present invention has been made in consideration of the above-mentioned background, and in a single-lens reflex camera in which a mirror moving motor is driven by supplying a pulse voltage subjected to pulse width modulation, the mirror is operated stably, and further, the motor An object of the present invention is to provide a single-lens reflex camera in which countermeasures are also taken against vibrations caused by driving.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, the present invention performs the pulse width modulation so that the pulse width of the pulse voltage gradually increases until the mirror is moved from the finder observation position to the photographing position. In addition to suppressing the occurrence, the degree of gradual increase of the pulse width can be changed by the pulse width control means. The degree of gradual increase of the pulse width of the pulse voltage is varied according to changes in the shooting conditions such as the voltage level of the driving power supply, the type of interchangeable lens used, and the presence or absence of the tilt mechanism. Appropriate pulse width modulation is performed.
[0013]
In addition, the motor is driven at a constant speed immediately before the mirror reaches the photographing position so as not to generate vibration accompanying the increase / decrease of the motor, which is effective in preventing camera shake during subsequent exposure. . In addition, the motor is driven at a constant speed immediately before the mirror reaches the shooting position, and the drive time can be varied depending on the type of lens and the presence or absence of the tilt mechanism, so that shooting is performed under conditions where vibration is likely to occur. In some cases, it is possible to prevent camera shake more effectively by shortening the motor acceleration period and lengthening the period during which the motor is driven at a constant speed so that there is no vibration from the motor itself. Can do.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows the appearance of a single-lens reflex camera using the present invention. This camera is a lens shutter type single-lens reflex camera using a Brownie film, and the entire system is composed of a camera body 2, a film holder 3, a lens holder 4 and a lens unit 5. The film holder 3 is attached to the camera body 2 via a mount portion having a revolving function, and the lens holder 4 is attached to the camera body 2 via a bellows 6. Further, a lens unit 5 is detachably attached to the lens holder 4. The lens holder 4 can be moved back and forth in the optical axis direction along a pair of guide rods 7 provided in the camera body 2, and focusing is performed by rotating the focus knob 8.
[0015]
As shown in FIG. 2, a mirror 10 and a light shielding plate 11 are pivotally mounted on the camera body 2, and subject light that has passed through the lens unit 5 is provided on the upper surface of the camera body 2 at the illustrated finder observation position. An image is formed on the focusing screen 12. Focusing can be performed by opening the finder hood 13 and operating the focus knob 8 while observing an image formed on the focusing screen 12. Since the light shielding plate 11 closes the aperture 14 at the viewfinder observation position, the film in the film holder 3 is not exposed.
[0016]
Electrical mount connectors are provided on the mount portion between the camera body 2 and the film holder 3 and the mount portion between the lens holder 4 and the lens unit 5, respectively. The electrical connection is made. The electrical connection between the camera body 2 and the lens holder 4 is made by a flexible cord 16.
[0017]
The film holder 3 incorporates a feeding motor, and is driven when exposure is completed by a signal from the camera body 2. The lens unit 5 has a built-in diaphragm whose aperture diameter can be changed by manual operation of the diaphragm setting knob 17, a magnet that keeps the shutter blades open during viewfinder observation, and a shutter time signal from the camera body 2. A shutter motor and a shutter blade that are driven originally are incorporated. When a release button 18 provided on the camera body 2 is operated, a series of shooting operations are executed under a predetermined sequence program stored in the memory of the camera body 2.
[0018]
FIG. 3 shows an outline of the electrical configuration. The camera body 3 incorporates a body control CPU 20 and controls a series of shooting operations according to a sequence program stored in the ROM area of the memory 21. A battery pack 22 is mounted on the camera body 2 as a power source. However, a power source switching circuit 24 is provided so that the AC power source 23 can be used. When the AC power source 23 is connected, the AC power source has priority over the battery pack 23. 23 is used.
[0019]
A constant voltage circuit 25 is connected to the power supply switching circuit 24, and the voltage level is determined by the battery check circuit 26. The battery check circuit 26 determines whether the voltage level is “OK level”, “warning level”, or “NG level”, and inputs the determination result to the main body control CPU 20. “OK level” is a level at which there is no problem even if the shooting operation is continued, “warning level” is a level at which at least 2 to 3 films can be shot as it is, and “NG level” is several frames It means a level that cannot guarantee the proper shooting operation. Information on the battery check is sent to the film holder 3 via the interface circuit 27 of the camera body 2 and displayed on the display panel 30 provided on the film holder 3. The input operation unit 31 inputs operation signals from various external operation members including the release button 18 to the main body control CPU 20.
[0020]
The mirror motor drive circuit 32 controls the drive of the mirror motor 33. By driving the mirror motor 33, the mirror 10 and the light shielding plate 11 are moved between the finder observation position and the photographing position. The shutter motor drive circuit 35 controls the drive of the shutter motor 36 built in the lens unit 5. The exposure time by the shutter blades is controlled by the control of the shutter motor 36. The shutter interface circuit 37 and the EEPROM interface circuit 38 are provided to exchange data between the main body control CPU 20, the shutter magnet 40 and the aperture mechanism 41 built in the lens unit 5, and the EEPROM 42. .
[0021]
The EEPROM 42 is used as a total shot counter that accumulates and counts the number of times the shutter built in the lens unit 5 is accumulated, and is also used as a storage unit for focal length data of the photographing lens 45 provided in the lens unit 5. . Data reading and writing from the EEPROM 42 are performed via the EEPROM interface circuit 38 by commands from the main body control CPU 20.
[0022]
The lens holder 4 attached to the camera body 2 has a tilt mechanism, and the bracket 46 attached with the lens unit 5 is shifted in the vertical and horizontal directions, or the optical axis of the photographing lens 41 is set in an arbitrary direction. Can tilt. Furthermore, a low-cost type lens holder that does not have the tilt mechanism can be attached to the camera body 2. The lens holder 4 is provided with a type signal unit 47 that indicates the presence or absence of the tilt mechanism, whereby the main body control CPU 20 determines whether or not the mounted lens holder 4 has the tilt mechanism. Can be identified.
[0023]
The film holder 3 incorporates a holder control CPU 48 and is connected to the camera body 2 via an interface circuit 49. A program for controlling the film holder 3 is stored in the ROM area of the memory 50, and the operation of the film holder 3 is controlled in accordance with command exchange and data exchange performed with the main body control CPU 20. A feeding motor drive circuit 51 controls driving of a feeding motor 52 for film feeding. The feeding motor 52 performs film feeding at the time of first frame setting when a film is newly loaded and film end feeding performed after shooting at the last frame, in addition to feeding one frame at each shooting. When driven.
[0024]
The film holder 3 is supplied with power from a dedicated lithium battery 53, but when connected to the camera body 2, it is supplied from the battery pack 22 or AC power supply 23 that supplies power to the camera body 2 via the power supply switching circuit 54. Operates with the power supply. A constant voltage circuit 55 is connected to the power supply switching circuit 54, and the voltage level is determined by the battery check circuit 56. Similarly to the battery check circuit 26 of the camera body 2, the battery check circuit 56 determines whether the voltage level is “OK level”, “warning level”, or “NG level”, and the determination result. Is input to the holder control CPU 48. The battery check information is displayed on the display panel 30 via the LCD drive circuit 57.
[0025]
The input operation unit 58 inputs operation signals from various setting input units provided in the film holder 3 to the holder control CPU 48. The signal from the input operation unit 58 includes, for example, an ISO sensitivity input signal of a film to be used, a signal for determining the necessity of date imprinting, a date correction input signal, a display signal for prompting display of the total number of shots, and a first frame set. There are various signals such as a signal to prompt
[0026]
FIG. 4 schematically shows an example of the mirror driving mechanism. This mirror driving mechanism is a well-known one whose detailed configuration and action are described in, for example, Japanese Patent Publication No. 7-60243. The mirror 10 and the light-shielding plate 11 which are stationary at the finder observation position shown in the figure are mirror motors 33. Are sequentially moved to the photographing position by the forward rotation of the lens, and after completion of the exposure, each is returned from the photographing position to the finder observation position by the reverse rotation of the mirror motor 33. Hereinafter, the operation of one cycle of the mirror 10 and the light shielding plate 11 will be described with reference to FIG.
[0027]
The mirror motor 33 starts normal rotation in response to a mirror operation signal output after it is confirmed that the shutter magnet 40 built in the lens unit 5 is turned on and the shutter blades are closed. When the mirror motor 33 starts normal rotation, the drive gear 62 rotates counterclockwise via the reduction gear 61. At the same time, the drive lever 63 fixed to the drive gear 62 rotates, the mirror drive pin 64 moves in the cam groove 65, and the cam lever 66 is slowly swung counterclockwise about the shaft 67.
[0028]
When the drive gear 62 continues to rotate counterclockwise, the mirror drive pin 64 moves to the tip side of the cam groove 65 and then moves to the base side of the cam groove 65 to further rotate the cam lever 66 counterclockwise. A mirror up lever 68 is pivotally attached to the shaft 67, and its rising edge 68b is engaged with the cam lever 66, so that the mirror lever 68 pivots counterclockwise when the cam lever 66 swings counterclockwise. To do. A pin 69 a fixed to the mirror holder 69 is engaged with a long hole formed at the tip of the mirror up lever 68, and the mirror 10 rotates about the shaft 70 by rotating the mirror up lever 68 counterclockwise. Turn clockwise. When the mirror driving pin 64 returns to the substantially central portion in the cam groove 65, the mirror 10 is moved to the photographing position rotated approximately 45 ° in the clockwise direction. At this time, the drive of the mirror motor 33 is temporarily stopped, but the mirror motor 33 continues to resume normal rotation.
[0029]
When the driving gear 62 is further rotated counterclockwise by the mirror motor 33, the light shielding plate 11 is rotated clockwise from the illustrated position around the shaft 70 via the light shielding plate driving mechanism (not shown) in conjunction with this. . When the mirror drive pin 64 moves to the base end of the cam groove 65, the light shielding plate 11 is also completely lifted, the aperture 14 is opened, and an exposure standby state is entered. The cam groove 65 has a shape in which two types of arcs are combined. Immediately after the mirror motor 33 is activated, the cam lever 66 rotates slowly, and after the mirror 10 moves to the photographing position, the mirror driving pin 64. However, even if the cam groove 65 is moved to the base side, the mirror 10 does not move from the photographing position.
[0030]
A fan-shaped signal plate 71 is fixed to the drive gear 62, and both edges thereof are detected by reflection type photosensors 72a and 72b. Then, at the moment when the mirror 10 is rotated to the photographing position, the photo sensor 72a detects the leading edge of the signal plate 71 and outputs a mirror up signal, and the drive gear 62 continues to rotate counterclockwise to shield the light. The photosensor 72b detects the leading edge of the signal plate 71 and outputs a light shielding plate up signal at the moment when the plate 11 reaches the photographing position. In response to this light shielding plate up signal, the driving of the mirror motor 33 is stopped.
[0031]
After the mirror 10 and the light shielding plate 11 are moved to the photographing position in this way, the shutter motor 36 incorporated in the lens unit 5 is actuated in response to a signal from the camera body 2, and photographing is performed. After the photographing is completed, the mirror motor 33 starts reverse rotation, and the drive gear 62 rotates clockwise. As a result, the mirror driving mechanism and the light shielding plate driving mechanism described above operate in opposite directions, respectively, and the light shielding plate 11 and the mirror 10 sequentially return from the photographing position to the viewfinder observation position. When the photo sensor 72b confirms that the signal plate 71 has returned to the position shown in FIG. 4, the driving of the mirror motor 33 is stopped and the camera body 2 turns off the shutter magnet 40 built in the lens unit 5. A signal is supplied, and the shutter blades are opened to return to the viewfinder observation state.
[0032]
The waveform of the drive voltage supplied when the mirror motor 33 is driven forward is shown in FIG. As shown in the figure, a pulse voltage having a constant voltage level determined by the constant voltage circuit 25 is supplied to the mirror motor 33, but the pulse width is narrow at the start-up, and the pulse width gradually increases with time. So that the pulse width is modulated. This pulse width modulation is performed by the main body control CPU 20 in accordance with the data stored in the ROM area of the memory 21.
[0033]
As shown in FIG. ₀ , Pulse width P _D Is P over time _D1 , P _D2 And then gradually widen and the period T ₀ Duty ratio D (= P _D / T ₀ ) Is gradually increased. In the pulse width modulation in the standard state, the degree of gradual increase of the duty ratio D is represented by a constant slope shown by a solid line in FIG. 8 and corresponds to the speed increasing period of the mirror motor 33. Then, after the speed increasing period, the duty ratio D becomes a constant value D1, and the constant speed driving period is reached. As a result, mechanical vibrations are less likely to occur when the mirror motor 33 is activated, and the mirror motor 33 is driven stably at a constant speed in the vicinity of the mirror 10 reaching the photographing position. Even if this occurs, it is not promoted and can be absorbed sufficiently.
[0034]
The main body control CPU 20 further constitutes pulse width control means for controlling the degree of the pulse width modulation, and has a function of adjusting the degree of increase of the duty ratio D. The solid line in FIG. 8 is the one when the voltage level of the power source determined by the battery check circuit 26 is “OK level”, and this is standard pulse width modulation. However, if the result of the battery check is “warning level”, the standard pulse width modulation is corrected, and the mirror motor 33 is driven according to the duty ratio increasing program as shown by the broken line in FIG. Done.
[0035]
When the battery pack 22 is attached to the camera body 2 and the power is consumed while shooting, or when the ambient temperature becomes low, the level of the output voltage from the constant voltage circuit 25 decreases, and the “NG level” , But may not reach the “OK level”. In such a case, it is displayed on the display panel 30 of the film holder 3 that the battery is “warning level”, and the pulse voltage supplied to the mirror motor 33 along with this is a pulse width as shown by a broken line in FIG. Modulation control is added.
[0036]
That is, the degree of gradually increasing the duty ratio D is determined according to a steeper slope compared with the standard pulse width modulation, and a pulse voltage having the duty ratio D2 is supplied to the mirror motor 33 after a predetermined time. Thereby, even if the voltage level of the pulse voltage is a “warning level” lower than the “OK level”, the electric energy per unit time supplied to the mirror motor 33 is kept at the same level as the “OK level”. Thus, the time required for the mirror 10 and the light shielding plate 11 to move from the finder observation position to the photographing position can be made substantially constant.
[0037]
Similar pulse width modulation control is performed during the drive period of the light shielding plate 11 performed after the mirror 10 is moved to the photographing position. However, since the light shielding plate 11 is driven immediately before exposure, it is more than when the mirror 10 is driven. By suppressing the driving speed of the mirror motor 33, vibration is less likely to occur. Note that since a single-lens reflex camera having a focal plane shutter device does not need to drive a light shielding plate, exposure may be performed after the reflex mirror is moved to the photographing position. Further, the control parameters necessary for the pulse width modulation control are written in the ROM area of the memory 21, and an appropriate control parameter is selected from the control parameters by the main body control CPU 20 according to the battery check level. Things will be read and used.
[0038]
The main body control CPU 20 also performs pulse width modulation control in the manner shown in FIG. 9 according to the type of the lens unit 5 used. The characteristic data of the lens unit 5 that can be used by being attached to the lens holder 4 is written in the EEPROM 42, and the main body control CPU 20 reads the characteristic data of the lens unit 5 through the EEPROM interface circuit 38. Then, pulse width modulation control of the pulse voltage supplied to the mirror motor 33 is performed according to the focal length of the lens unit 5 being used.
[0039]
When the lens unit 5 has a standard focal length, standard pulse width modulation shown by a solid line is performed. However, when the lens unit 5 has a long focal length, it is indicated by a broken line, and when it has a short focal length, it is indicated by a dashed line. Corrections are made to the standard pulse width modulation so that the duty cycle increase program is correct. Since the lens unit with a long focal length has a long lens length, vibrations generated during the speed-up process of the mirror motor 33 tend to be sustained. In order to cope with this, when using a lens unit having a long lens length, as shown by a broken line in FIG. 9, the mirror motor 33 finishes accelerating earlier and takes a longer driving period at a constant speed at which vibration is less likely to occur. To ensure.
[0040]
Further, it is preferable to correct the pulse width modulation depending on whether or not the lens holder 4 has a tilt mechanism. The lens holder 4 is provided with a type signal unit 47, whereby the main body control CPU 20 can identify whether or not the lens holder 4 being used has a tilt mechanism. Then, when it is confirmed that the tilt mechanism is provided, the same correction as that for the long focal length shown by the broken line in FIG. 9 is applied, and when the lens holder 4 having no tilt mechanism is used, The same pulse width modulation control as that for the standard focal length is performed. When the tilt operation is performed, the weight balance of the entire camera system is easily lost, and it tends to be difficult to attenuate when vibration occurs. Therefore, as described above, it is advantageous to shorten the speed increasing period of the mirror motor 33 and increase the driving period at a constant speed.
[0041]
Any one of the various pulse width modulation controls described above may be used, but can be used in combination by performing the processing shown in FIG. Hereinafter, the operation when these pulse width modulation controls are used in combination will be described. When the shooting sequence is started by pressing the release button 18, the shutter magnet 40 is turned on and the shutter blades are closed. Upon receiving the shutter blade closing signal, the main body control CPU 20 outputs a mirror operation start signal, and a battery check is first performed. Although the battery check has already been performed when the power switch of the camera body 2 is turned on, the output voltage level of the constant voltage circuit 26 is rechecked by the battery check circuit 26 when the mirror operation start signal is output.
[0042]
As a result of the battery check, when the “NG level” has not been reached, the processing is ended as it is, and a display for prompting replacement or switching of the battery is performed. When the voltage level from the constant voltage circuit 26 is equal to or higher than the “NG level” and exceeds the “warning level”, it becomes “OK level”, and under the standard pulse width modulation shown by the solid line in FIG. 33 is driven. When it is below the “warning level”, the control parameter written in the ROM area of the memory 21 is read by the main body control CPU 20 in order to perform the pulse width modulation processing indicated by the broken line in FIG. Is written at a predetermined address position.
[0043]
Next, the characteristic data of the lens unit 5 mounted on the lens holder 4 is read from the EEPROM 42, and it is identified whether the photographing lens has a standard focal length, a long focal length, or a short focal length. When the identified focal length is a long focal length or a short focal length, the control parameters for pulse width modulation control indicated by the broken line or the alternate long and short dash line in FIG. 9 are read and similarly written in the RAM area of the memory 221. It is.
[0044]
Further, whether or not the lens holder 4 being used has a tilt mechanism is identified by the data from the identification signal section 47 of the lens holder 4, and when there is a tilt mechanism, a pulse indicated by a broken line in FIG. Control parameters for driving the mirror motor 33 under width modulation are prepared.
[0045]
As described above, after the battery check, the focal length identification of the used lens unit, and the presence or absence of the tilt mechanism are sequentially confirmed, the degree of pulse width modulation of the pulse voltage supplied to the mirror motor 33 is determined. When the result of the battery check is “OK level”, the lens unit 5 has a standard focal length, and the lens holder 4 does not have the tilt mechanism, the solid line is shown in FIG. 8 or FIG. The mirror motor 33 is driven by standard pulse width modulation.
[0046]
In other cases, the control parameters written in the RAM area of the memory 21 are read by the battery check, the focal distance, and the presence / absence of the tilt mechanism, and the calculation process is performed based on these control parameters. To determine the control parameters. The standard pulse width modulation is corrected under the control parameters thus determined, and the pulse width modulation of the pulse voltage supplied to the mirror motor 33 is performed.
[0047]
According to the above, when the mirror motor 33 is driven with a pulse voltage subjected to pulse width modulation, exposure is performed in a state in which the degree of pulse width modulation is adjusted according to various imaging conditions and the influence of mechanical vibration is significantly reduced. Will come to be. Therefore, it is possible to eliminate camera shake accompanying the mirror operation unique to a single-lens reflex camera and camera shake caused when the light shielding plate is retracted in a lens shutter type camera.
[0048]
Although the present invention has been described according to the illustrated embodiment, the present invention can be equally applied not only to a single-lens reflex camera using a brownie film but also to a single-lens reflex camera using an IX240 film for 135 film or APS. is there. In addition, for example, when there are many types of interchangeable lenses having standard focal lengths, long focal lengths, and short focal lengths as well as many types of focal lengths, they are classified into three types according to the focal lengths. In addition to the identification, finer identification may be performed and a control parameter for pulse width modulation may be used for each focal length.
[0049]
Further, for the lens holder having the tilt mechanism, the pulse width modulation may be corrected depending on whether or not the tilt operation is actually performed. Also, the pulse width gradual increase processing by pulse width modulation is not only linearly increased as in the above embodiment, but can also be increased non-linearly. It is also possible to switch between processing and non-linear gradual processing.
[0050]
The present invention is not limited to the above-described fluctuations in the power supply voltage level, changes in the type of photographing lens, and fluctuations in photographing conditions such as the presence or absence of a tilt mechanism. On the other hand, it is possible to effectively apply to various other shooting condition fluctuations, such as varying the gradual increase of the pulse width when driving the reflex mirror based on the subject distance or the protruding length of the lens. It is.
[0051]
【The invention's effect】
As described above, in the single-lens reflex camera of the present invention, when the motor is driven by supplying a pulse voltage modulated with pulse width and the reflex mirror is moved using the rotation, the voltage level of the power source, the lens used The imaging conditions such as focal length and tilt mechanism are identified, and the pulse width modulation of the pulse voltage supplied to the motor is controlled according to these various imaging conditions. The time until the camera is retracted from the position to the photographing position is kept substantially constant, and the influence of mechanical vibration associated with the driving of the reflex mirror can be eliminated and photographing without camera shake can be performed.
[Brief description of the drawings]
FIG. 1 is an external view of a single-lens reflex camera using the present invention.
FIG. 2 is a cross-sectional view of a main part of the camera shown in FIG.
3 is a block diagram showing an outline of an electrical configuration of the camera shown in FIG. 1. FIG.
FIG. 4 is a schematic diagram illustrating an example of a mirror driving mechanism.
FIG. 5 is a time chart showing an outline of a photographing sequence.
FIG. 6 is a waveform diagram showing an outline of a pulse voltage supplied to the mirror motor.
FIG. 7 is an explanatory diagram of pulse width modulation.
FIG. 8 is a program diagram of a duty ratio according to a battery check level.
FIG. 9 is a program diagram of a duty ratio according to the focal length of a lens used.
FIG. 10 is a flowchart showing processing of pulse width modulation control.
[Explanation of symbols]
2 Camera body
3 Film holder
4 Lens holder
5 Lens unit
10 Mirror
11 Shading plate
33 Mirror motor
64 mirror drive pin
65 Cam groove
66 Cam lever
68 Mirror up lever

Claims (4)

The motor is driven by intermittently supplied pulse voltage, and the motor is driven to move the reflex mirror between the viewfinder observation position and the shooting position, and the reflex mirror is moved from the viewfinder observation position to the shooting position. In a single-lens reflex camera in which pulse width modulation is applied so that the pulse width of the pulse voltage gradually increases,
Depending on the type of photographic lens used, pulse width control means was provided to control the pulse width modulation while moving the reflex mirror from the finder observation position to the photographic position, and to change the degree of gradual increase of the pulse width. SLR camera featuring The motor is driven by intermittently supplied pulse voltage, and the motor is driven to move the reflex mirror between the viewfinder observation position and the shooting position, and the reflex mirror is moved from the viewfinder observation position to the shooting position. In a single-lens reflex camera in which pulse width modulation is applied so that the pulse width of the pulse voltage gradually increases,
Controls pulse width modulation while moving the reflex mirror from the viewfinder observation position to the shooting position based on whether the lens holder that holds the shooting lens has a tilt mechanism, and changes the degree of gradual increase of the pulse width. A single-lens reflex camera comprising a pulse width control means. The pulse width control means is characterized in that the pulse width of the pulse voltage is kept constant for a predetermined period immediately before the reflex mirror reaches the photographing position, and the predetermined period is variable according to the type of the photographing lens. The single-lens reflex camera according to claim 1 . The pulse width control means keeps the pulse width of the pulse voltage constant for a predetermined period immediately before the reflex mirror reaches the photographing position, and the predetermined period is variable based on whether the lens holder has a tilt mechanism. The single-lens reflex camera of Claim 2 characterized by the above-mentioned .

Images