JP2006091136A - Motor drive method for digital camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mirror drive method preventing image data from being noised when taking in an image in a digital single-lens reflex camera, in which a mirror is moved upward and downward by using a motor. <P>SOLUTION: The digital single-lens reflex camera having the mirror 37 moved to an observing position in which subject light made incident on from a photographic lens 100 is reflected towards the optical system 71 of an optical finder and to an imaging position in which the subject light is allowed to be made incident on an imaging element 55. In the digital single-lens reflex camera, the drive method for the mirror motor 33 for moving the mirror 37 from the observing position to the image position and from the imaging position to the observing position includes greatly altering a duty ratio stepwise after the start of the supply of power under a PWM control with a small duty ratio when the mirror motor 33 is started. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a motor driving method for a digital camera.

A single-lens reflex camera is known as a mirror device that raises / lowers a so-called quick return mirror by driving a motor. In a single-lens reflex camera equipped with a motor-driven mirror device, when the release starts, the motor is energized to raise the mirror and stop in the up state, and then the shutter (focal plane shutter) is opened to start exposure, and the shutter It closes and completes exposure, and then energizes the motor to lower the mirror and performs so-called mechanical charging (Patent Document 1).
Japanese Patent Laid-Open No. 10-142686

  However, in the conventional motor-driven mirror device, a rush current is generated at the moment when energization of the motor is started in order to raise or lower the mirror, and this rush current causes the power supply circuit of the single-lens reflex camera. Excessive load is applied, causing malfunction. In particular, in so-called digital single-lens reflex cameras, noise is generated due to the effect of the rush current when the motor of the mirror device is driven, and the noise overlaps with the image capture, resulting in band-like disturbances in the image. .

  The present invention has been made in view of the problem of a mirror device that raises and lowers a mirror with a motor in a digital single-lens reflex camera. An object of the present invention is to provide a motor driving method that reduces noise generation and prevents noise from entering an image signal. And

  The present invention that achieves this object is a method for driving a motor mounted on a digital camera. When starting the motor, the duty ratio is increased stepwise after starting energization by PWM control with a small duty ratio. It is characterized by significant changes.

  The invention applied to a digital single-lens reflex camera provided with a mirror that moves subject light incident from a photographing lens to an observation position that reflects in the direction of the optical viewfinder and an imaging position that allows incidence to the imaging means. A method of driving a motor that moves from an observation position to an imaging position and from an imaging position to an observation position. When the motor is started, the duty ratio is stepwise after starting energization with PWM control with a small duty ratio. It is characterized by significant changes.

Further, according to the method of the present invention, when a predetermined time elapses after energization of the motor by PWM control with a small duty ratio, DC energization is performed, or energization is started after PWM energization with a small duty ratio is started. The duty ratio is greatly changed step by step until it becomes.
Thus, according to the method of the present invention, when the motor being driven is stopped, the reverse brake for PWM control is applied before the start and the end. In the reverse brake by the PWM control, the duty ratio is gradually changed from small to large during the period when the reverse brake is started, and the duty ratio is gradually changed from large to small during the period before the reverse brake is finished. The reverse brake applies a DC reverse brake between a predetermined period when the reverse brake starts and a predetermined period before the reverse brake ends.

According to the present invention, when the motor is started, energization is started by PWM control, and the duty ratio is increased stepwise, so that a rush current does not flow when the motor is started, and voltage drop and noise are suppressed. It becomes possible.
If the present invention is applied to a digital camera having a mirror device that moves subject light incident from a photographing lens to an observation position that reflects in the direction of the optical viewfinder and an imaging position that allows incidence to the imaging means, the rush current The influence on the image signal due to is eliminated, and there is no possibility that noise is mixed in the image signal.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a block diagram showing a circuit configuration of a digital single-lens reflex camera to which the present invention is applied, and FIG. This digital single-lens reflex camera includes a mirror 37 that moves to an observation position where the subject luminous flux incident from the photographing lens 100 is reflected toward the viewfinder optical system 71 and an imaging position where the subject luminous flux is incident on the image sensor 55 (FIG. 2). In this embodiment, the mirror 37 is moved between the observation position and the imaging position by the mirror motor 33.

  This digital single-lens reflex camera includes, as a control system, a CPU 11 that controls the overall operation of the camera, a DPU 13 that mainly controls input of a mode setting switch, and a DSP 15 that mainly performs image processing. . These CPU 11, DPU 13 and DSP 15 operate in communication with each other under the control of the CPU 11. The CPU 11, the DPU 13 and the DSP 15, and various electronic components controlled by them are operated by the power supplied through the battery 17 and the power supply circuit 19. The power supply circuit 19 is controlled by the DPU 13.

  The DPU 13 controls charging and light emission of the external strobe 20 and the built-in strobe 21, checks the on / off state of the mode dial 23 and various switches 25, and executes control according to the on / off state. The DPU 13 supplies power to the mounted photographing lens 100 and communicates information such as an aperture and a focal length with the photographing lens 100. Further, the DPU 13 controls the operation of the AFIC 29 which is a so-called passive phase difference focus detection sensor. The AFIC 29 splits and receives the subject light, which is transmitted through the half mirror portion of the mirror 37 and reflected by the sub-mirror 38, through the pupil division optical system among the subject light incident through the photographing lens 100 (see FIG. 2). ), And outputs a video signal related to the phase difference of the subject image to the CPU 11.

  The CPU 11 obtains the defocus amount based on the video signal input from the AFIC 29, obtains the drive direction and drive amount of the focus adjustment lens group (not shown) of the photographing lens 100, and uses the AF motor 41 through the AF motor driver 39. To drive the focusing lens group to the in-focus position. The driving amount of the AF motor 41 is detected by counting the peripheral force pulse signal of the AF control photo interrupter 43 that outputs a pulse signal in conjunction with the rotation of the AF motor 41. Further, the CPU 11 inputs the subject luminance signal from the divided photometry IC 45 and calculates the shutter speed and the aperture value.

  The mirror 37 is supported by the mirror drive mechanism 34 so as to be movable between an observation position where the subject light incident from the photographing lens 100 is reflected toward the viewfinder optical system 71 and an imaging position where the light is incident on the CCD image sensor 55. Yes. This mirror drive mechanism 34 is driven by a mirror motor 33. The CPU 11 drives and controls the mirror motor 33 via the mirror motor driver 31. The mirror drive mechanism 34 of this embodiment is a mechanism that moves up from the observation position to the imaging position and moves down from the imaging position to the observation position by forward rotation of the mirror motor 33. The mirror 37 switches the position of the mirror 37 by the mirror detection switch 35. Detect. The mirror detection switch 35 of this embodiment includes a mirror up switch SWMRUP that detects that the mirror is up to the imaging position and a mirror down switch SWMRDN that detects that the mirror is down to the observation position. .

  Although not shown in detail, the mirror driving mechanism 34 in this embodiment raises the mirror 37 from the imaging position to the observation position and lowers the imaging position to the observation position by one-way rotation of the mirror motor 33. The mirror up switch SWMRUP is composed of a brush interlocking with the rotation of the mirror motor 33, and a code plate provided with a conductive portion and a nonconductive portion in sliding contact with the brush. When the mirror 37 is at the observation position, When the mirror 37 rotates from the observation position toward the imaging position, the mirror 37 becomes low level during the rotation, becomes high level near the imaging position, and becomes low level at the imaging position. In the mirror down, when the mirror 37 is rotated from the imaging position to the observation position, the mirror 37 once becomes a low level in the middle of the rotation and then becomes a high level again. When the mirror is lowered to the observation position, the low level is maintained.

  The CPU 11 inputs a set shooting mode, various shooting correction values and the like from the EEPROM 47 which is a nonvolatile memory means, and sets the shooting conditions such as the shooting mode to an external display LCD (liquid crystal display) 51 provided outside the camera. The image is displayed on the LCD (liquid crystal display) 53 in the viewfinder. The LCDs 51 and 53 include illumination LEDs 51a and 53a.

  The CPU 11 includes, as switches, an Av dial switch 59 for manually setting an aperture value, a Tv dial switch 61 for manually setting a shutter speed, a switch 63 including a main switch (power switch) SWM for turning on / off the power, and a shutter. A switch 65 is connected. The shutter switch 65 includes a photometric switch SWS that is turned on when the shutter button is half-pressed and a release switch SWR that is turned on when the shutter button is fully pressed.

  Further, the CPU 11 controls driving of the shutter 49. Although not shown in detail, the shutter 49 is a focal plane shutter, and mechanically locks the travel of the front curtain and the rear curtain by a spring for traveling the front curtain and the rear curtain, and a charged spring. A shutter locking mechanism interlocked with the mirror 37, and shutter magnets ESMg1 and ESMg2 for electromagnetically locking the front curtain and the rear curtain in place of the locking of the shutter locking mechanism are provided.

  When the mirror is raised and the shutter 49 is opened, a subject image is formed on the light receiving surface of the image sensor 55 by the photographing lens 100. The image sensor 55 receives a subject image with a number of light receiving elements, converts it into an electrical image signal, and outputs it to the DSP 15. The DSP 15 performs predetermined correction such as white balance correction on the input image signal, displays it on the image LCD 57, converts it into a preset image format, and writes it in the CF card 67. The image LCD 57 is usually mounted on the back of the camera body and includes an illumination LED 57a. The flash memory 69 stores firmware related to camera operation, imaging operation, etc., and the DSP 15 reads it when the power is turned on.

  Next, the photographing operation of this digital single lens reflex camera will be described with reference to the timing charts shown in FIGS. 3 and 4 and the flowcharts shown in FIGS. FIG. 3 is an overall timing chart regarding the release process of the digital single-lens reflex camera, and FIG. 4 is a timing chart regarding the operation of the mirror motor 33 in the release process.

  5 and 6 are main flowcharts relating to the entire camera process. This process is entered when the battery 17 is loaded. When the entire camera process is entered, hard initialization such as initialization of each input / output port is first executed (S2), the built-in RAM is all cleared, and software initialization such as constant setting and correction value reading is executed (S4). . Thereafter, the power supply other than the power supply of the main control system such as the CPU 11 is turned off (S6), all the display LCDs are turned off (S8), and the main switch OFF loop process is started.

“Main switch SWM; OFF”
The main switch OFF loop process is a process that is periodically repeated while the main switch SWM is OFF. In this process, first, the on / off states of all the switches 63 are input (S10), and it is checked whether or not the main switch SWM is ON (S12). When the main switch SWM is not ON (S12; N), a 250 mS timer interrupt is set (S14), the CPU 11 is shifted to the standby mode (S16), and when 250 mS elapses, the CPU 11 is activated (S18), and the process goes to S10. Return. That is, while the main switch SWM is OFF, this main switch OFF loop process is repeated every 250 ms.

“Main switch SWM; ON”
When the main switch SWM is turned on (S12; Y), in preparation for the start of the main switch ON loop processing or the jump by the battery NG from the power ON loop processing, first the power OFF processing is executed (S20), The photometry timer OFF loop processing is entered.

“Photometric timer OFF loop processing”
When the photometry timer OFF loop processing is entered, information relating to the camera state such as the number of images that can be taken, the battery state, the image size, and the white balance (WB) is lit on the external display LCD (S22). Next, all switch states including the main switch SWM, photometric switch SWS, and release switch SWR are input (S24), and it is checked whether the main switch SWM is ON (S26). If the main switch SWM is not ON (S26; N), the process returns to S6, but when the main switch SWM is ON (S26; Y), lens information is input by CPU-lens communication (S28), Camera information such as switch information and battery information is communicated to the DSP by CPU-DSP communication (S30), photometry switch SWS interrupt is permitted (S32), an interrupt by a 250 mS timer is set (S34), and CPU standby mode is entered. (S36). It is checked whether or not there has been an interruption by the photometric switch SWS (the photometric switch SWS has been turned on) (S38). If there is no interruption by the photometric switch SWS (S38; N), it waits for 250 mS to elapse (S40), and when it elapses, the CPU 11 starts and returns to S22. The above processing is repeated until the main switch SWM is turned off or the photometric switch SWS is turned on. When the main switch SWM is turned OFF (S26; N), the process returns to S6.

“Photometry switch SWS; ON”
When there is an interruption by the photometry switch SWS (S38; Y), the power used for the 16-division photometry IC 46, AFIC 29, external display LCD 51, etc. is turned on (S42), photometry by the 16-division photometry IC 46, and focus detection by the AFIC 29 Then, a display operation is performed by the external display LCD 51 or the like. Then, the photometric 10 second timer is started (S44), and the photometric timer ON loop processing is started. The photometric timer is a timer that measures the time for returning to S20 when a predetermined time elapses with the photometric switch SWS turned off.

“Photometry switch timer ON loop processing”
When the photometry timer ON loop processing is entered, the on / off state of all switches is input (S46), and it is checked whether the main switch SWM is ON (S48). If the main switch SWM is not ON (S48; N), the process returns to S6, and when it is ON (S48; Y), the following loop processing is executed.

“Main switch SWM: ON, metering switch SWS; ON”
Lens information is input by CPU-lens communication (S50). The subject luminance Bv signal input from the 16-divided photometry IC 46 is A / D converted, the appropriate shutter speed and aperture value are calculated by AE calculation (S54), and the shutter speed calculated by AE calculation is added to the display information when the power is off. Further, the display of the aperture value and the like, the finder LCD 53 and the illumination LED 53a are also turned on (S56), and the photometric calculation values (shutter speed and aperture value) are communicated to the DSP 15 by CPU-DSP communication (S58). Then, the 125 ms timer is started (S60), and the release switch SWR interrupt is permitted (S62).

It is checked whether or not 125 mS has elapsed (125 mS timer has timed up) (S64), and when it has not elapsed (S64; N), it is determined whether or not the photometric timer time (photometric 2-second timer or 10-second timer) has elapsed. It is checked (S66), and if it has not elapsed (S66; N), it is checked whether or not the photometric switch SWS is ON (S68). When the metering switch SWS is ON (S68; Y), AF processing is executed (S80), and when it is not ON (S68; Y), S80 is skipped and there is a release interrupt (release switch) It is checked whether SWR is turned on (S70). If there is no release interrupt (S70; N), the process returns to S64. That is, the processes from S64 to S70 are repeated until 125 mS has elapsed. When 125 mS has elapsed (S64; Y), the process returns to S46, and the processes from S46 to S62 and S64 to S70 are executed.
"Release switch SWR; ON"
If the release switch SWR is ON during the photometry timer ON loop processing, that is, if a release interrupt is received (S70; Y), the mirror up processing (S72) is executed, the exposure processing (S74) is executed, After executing the charging process (S78), after exposure, a photometric 2-second timer is started to display the photometric value for 2 seconds (S78). Then, the process returns to S46, and the processes from S46 to S80 are repeated. In this embodiment, if the release switch SWR is kept ON, the photometry process (S52, S54), the AF process (S68; Y, S80) and the exposure process (S70; Y, S72 to S78, S46) are repeated. On the other hand, when the release switch SWR is turned OFF, when the photometry 2-second timer time set as the photometry timer time has elapsed (S66; Y), the process returns to S20, the power OFF process is executed, and the photometry timer OFF loop process is repeated.

Mirror up process
The mirror-up process executed in S72 will be described with reference to the flowcharts shown in FIGS. In this flowchart, the mirror motor state identifies the state of the mirror motor as follows.
Mirror motor state 0: PWM drive at start of operation (forward rotation)
1: DC drive (forward rotation)
2; During primary braking 3; During DC drive (forward rotation)
4: During reverse braking 5: During secondary braking

  In this process, first, the shutter magnets ESMg1 and ESMg2 are energized to electromagnetically lock the shutter front curtain and rear curtain (S102). The photometry value Bv is input from the divided photometry IC 45, and the latest photometry value Bv is A / D converted (S104), the shutter speed and aperture value are calculated by AE calculation (S106), and the calculated shutter speed and aperture value are set for each. The data is displayed on the LCDs 51 and 53 (S108). Then, the 200 μS reference timer is started (S110). The 200 μS reference timer is a hard timer built in the CPU 11 and is used for measuring shutter speed (exposure time), brake time, mirror switch SW change timing, and the like.

For the moving object prediction calculation, the mirror up time measurement timer is started (S112), and the mirror up start is transmitted to the DSP 15 by CPU-DSP communication.
It is checked whether or not the aperture is open (S116). If the aperture is open (S116; Y), the aperture magnet EEMg is turned on (S118), and the aperture is held open. If the aperture is not open (S116; N), The EEP count is set, the EEP narrowing is permitted (S120), the chattering removal variable of the mirror up switch SWMRUP, the variable for the mirror up switch SWMRUP count, the variables such as the motor state and constants are initialized (S122), and the mirror motor 33 The mirror stop flag that is set to “1” when the camera stops is cleared (S124). When the EEP count setting and EEP narrowing are permitted, the aperture pulse (EEP) output from the unillustrated narrowing mechanism that operates in conjunction with the mirror up is counted, and when the count value matches the EEP count, the aperture magnet The EEMg is turned on to stop the narrowing mechanism.

“Mirror motor start; PWM control start; Mirror motor state 1; FIG. 4A”
Then, energization by PWM control is started to the mirror motor 33 (S126). In this embodiment, the PWM control cycle (one pulse cycle) is set to 100 μS, and when PWM control is started from the OFF state, the lowest duty ratio (0 percent) is started, and the duty ratio is set to periodic (200 μS). When the DC control is started with the stepwise change (by several percent) every time and the PWM control is started from the DC drive state, the duty ratio is changed periodically (200 μS), starting from the highest duty ratio (100%). Every step) and change it off step by step (by a few percent). Thus, since the mirror motor 33 is started by PWM control with the minimum duty, a rush current does not flow and an excessive burden is not imposed on the power supply circuit 19. In the illustrated embodiment, so-called single shooting is performed, but the PWM control processing at the time of starting and stopping of this embodiment is effective when the image processing circuit operation overlaps with the mirror-up processing in continuous shooting. .

  “0” is set in the mirror motor state (S128), and it is checked whether “1” is set in the mirror stop flag (S130). The mirror stop flag is a flag that is set when it is detected that the mirror has stopped. When the mirror stop flag is set to “1” (S130; Y), that is, when the mirror up is completed, AE calculation for flash emission is executed (S204), and the flash data final communication with the external flash is executed. (S206), TTL integration start preparation is executed (S208), mirror-end completion is transmitted to the DSP 15 by CPU-DSP communication (S210), mirror-up time measurement is terminated, and the measurement time is stored as a measured value. (S212), return.

  While the mirror stop flag is not set to “1” (S130; N), the following loop processing is repeated every 200 μS.

  The level of the mirror up switch SWMUP is checked (S132). When the same level is detected five times in succession, it is determined that the edge of the mirror up switch SWMUP is switched, and 1 is added to the number of edges of the mirror up switch SWMUP. Then, 1 is added to the mirror up time measurement counter (S134). The brake time count soft counter is decremented by 1 (S136). The brake time count soft counter is a counter for measuring the primary brake time.

  Then, it is checked whether or not the mirror motor status flag is “0” (S138). When the mirror motor status flag is “0” (S138; Y), the PWM control is being performed, so the DUTY change process is executed (S140). The DUTY change process is a process for increasing the duty of the PWM control step by step. In this embodiment, the duty is increased every 200 μS.

  It is checked whether the PWM control time has ended (S142). The PWM control time in this embodiment is 5 mS. Before the PWM control time elapses (S142; N), S144 and S146 are skipped, and it is checked whether the edge of the mirror up switch SWMUP is “1”, that is, whether the first edge of the mirror up switch SWMUP is detected. (S148). If the first edge has not been detected (S148; N), it waits for 200 μS to elapse (S156; N), and after 200 μS has elapsed (S156; Y), returns to S130 and repeats the loop processing from S130 to S156. .

"PWM control time end, DC drive, mirror motor state 1"
When the PWM control time is over (S142; Y), the drive of the mirror motor 33 is switched to the forward rotation drive by DC (direct current) (S144), and “1” is set in the mirror motor state (S146). Then, the process returns from S148; N through S156 and S130 to the mirror motor state check in S138.

  Since “1” is set in the mirror motor state in S146 (S138; N), the process proceeds to S158 to check whether the mirror motor state is “1”. Here, since the mirror state is “1” (S158; Y), the process returns to S148. That is, the DC drive of the mirror motor 33 is repeated until the first edge of the mirror up switch SWMUP is detected (S148; N, S156; Y, S130; N, S132 to S138; N, S158; Y, S148; N ).

“Edge detection of SWMUP status signal, primary brake, mirror motor status 2”
When the edge of the status signal of the mirror up switch SWMUP is detected once (S148; Y), the primary brake is applied to the mirror motor 33 (S150). Here, the primary brake is to short-circuit the power terminal of the mirror motor 33. Then, the primary brake time, which is the time during which the primary brake is continuously applied, is set (S154), and “2” is set to the mirror motor state (S154).

  When “2” is set in the mirror motor state, the process proceeds to a check (S160) as to whether or not the mirror motor state is “2” through a mirror motor state check process (S138; N, S158; N). Here, since the mirror motor state is “2” (S160; Y), it is checked whether or not the primary brake time soft counter decremented in S136 has become 0 (whether or not the primary brake has ended) (S162). If the primary brake has not ended (S162; N), it is checked whether the edge of the status signal of the mirror up switch SWMUP has been detected three times (S168). If not detected three times (S158; N), S156; Y, S130; N to S138; N, S160; Y, S162; N, S168; N, S156 every 200 μS until the primary brake is completed Repeat the process. Normally, the primary brake is completed and the primary brake is finished before the edge of the state signal of the mirror up switch SWMUP is detected three times.

"Primary brake time elapsed, DC drive, mirror motor state 3"
When the primary brake time has elapsed and the primary brake is finished (S162; Y). The mirror motor 33 is DC forward driven (S164), and "3" is set to the mirror motor state (S166). Then, until the number of edges of the mirror up switch SWMUP becomes 3, S168; N, S156; Y, S130; N to S138; N, S158; N, S160; N, S176; Y, S168; N, the loop process of S156 is repeated.

“Mirror up switch SWMRUP edge 3 times, PWM reverse brake, mirror motor state 4; B in FIG. 4”
When the number of edges of the mirror up switch SWMUP becomes 3 (S168; Y), the reverse PWM brake is applied to the mirror motor 33 (S170), the reverse brake time is set (S172), and the mirror motor state is set to “4”. "Is set (S174). When 200 μS elapses (S156; Y), S130; N to S138; N, S158; N, S160; N, S176; N, S178; Y to S180, and duty change processing is executed. The duty change process here is a process for changing the duty ratio to be smaller stepwise every time 200 μS elapses.

“PWM reverse brake 5ms before PWM reverse brake start”
Then, the duty changing process (S180) is repeated every 200 μS until 5 mS (first brake time) has elapsed after the start of the PWM reverse brake (S182; N, S186; N, S190; N, S156; Y). , S130; N to S138; N, S158; N, S160; N, S176; N, S178; Y to S180, S182). In S182, the mirror motor soft counter is used to check whether 5mS (first brake time) has elapsed since the start of PWM reverse rotation braking. In S186, the mirror motor soft counter is checked to determine whether it is 5mS before the end of braking. In S190, reverse braking is performed. Check if the time is over.

“5mS after brake start, mirror motor reverse DC brake”
When 5 mS elapses after the start of the PWM reverse rotation brake (S182; Y), switching to the mirror motor reverse rotation DC brake is performed (S184). Then, the mirror motor reverse DC braking is continued (S186; N, S190; N, S156; Y, S130; N to S138; N, S158; N, S160; N, S176; N, S178; Y, S180. S182; Y, S184, S186; N).

“5mS before reverse brake time ends”
When 5 mS is reached before the end of the brake time (S186; Y), the reverse DC brake is switched to the reverse PWM brake (S188). Then, this reverse PWM brake process is repeated every 200 μS (S, repeat until the reverse brake time ends (S190; N, 156; Y, S130; N to S138; N, S158; N, S160; N , S176; N, S178; Y, S180, S182; N, S186; Y, S188, S190; N) The duty change processing (S180) in this loop processing is performed step by step every 200 μS elapses. Is a process of reducing the power supply time (shortening the energization ON time).

"After reverse rotation braking time, mirror motor state 5"
When the reverse brake time ends (S190; Y), the secondary brake is applied to the mirror motor 33 (S192). This secondary brake is a process of short-circuiting the power supply terminal of the mirror motor 33 as in the case of the primary brake. Then, the secondary brake time is set (S194), and "5" is set to the mirror motor state (S196). Then, when 200 μS has passed (S156; Y), S130; N to S138; N, S158; N, S160; N, S176; N, S178;

  In S198, it is checked whether or not the secondary brake time has ended. If it has not ended (S198; N), the process returns to S156. Then, the check of whether or not the secondary brake time has ended is repeated every 200 μs (S156; Y, S130; N to S138; N, S158; N, S160; N, S176; N, S178; N S198; N, S156). When the secondary brake is finished (S198; Y), the mirror motor 33 is set free, that is, the power supply terminal is opened (S200), the mirror motor stop flag is set to "1" (S202), and the process proceeds to S156. Thus, when the mirror up is completed, “1” is set to the mirror motor stop flag.

“Mirror up complete, mirror motor stop flag“ 1 ””
When “1” is set in the mirror motor stop flag (S130; Y), the mirror up end is transmitted to the DSP 15 by CPU-DSP communication (S210), the mirror up time measurement is finished and the measurement time is measured. Save as a value (S212) and return.

`` Mecha charge processing ''
Next, the mechanical charge process executed after the exposure will be described with reference to the flowcharts shown in FIGS. The end of the exposure processing is when the energization of the shutter (rear curtain) magnet ESMg2 is turned off after the exposure time has elapsed.

  First, it waits for a time (20 mS) for the trailing curtain to completely travel (S302). When 20 mS elapses, CPU-DSP communication for transmitting the start of mechanical charge is executed (S304), and mechanical charge is started.

  A variable for chattering removal of the mirror dyne switch SWMRDN, a variable for counting the mirror down switch SWMRDN, a variable such as a motor state, and constants are initialized (S306), and measurement of mirror down time is started for moving object prediction calculation (S308). Then, a 200 μS reference timer that counts 200 μS serving as a reference for brake time, mirror switch check timing, and the like is started (S310).

“Mirror motor start-up; PWM drive control start; Mirror motor state 0; FIG. 4C”
The mirror motor 33 is normally rotated by PWM drive (S312). The PWM period is set to 100 μS. The duty at the time of PWM drive start-up is a setting with the shortest ON time. The mirror motor state is set to “0” (S314), and the mirror motor stop flag is cleared (“0” is set) (S316). Then, the loop processing after S318 is repeated until the mirror motor stop flag is set to “1”.

  In S318, it is checked whether or not “1” is set in the mirror motor stop flag. Since “0” is initially set in S316 (S318; N), the process proceeds to S320 and subsequent steps. While the mirror motor stop flag is set to “0” (S318; N), the following loop processing is repeated. If “1” is set in the mirror motor stop flag (S318; Y), the end of the mechanical charge is transmitted to the DSP 15 by CPU-DSP communication (S392), and the mirror down time measurement is completed. The measurement time is stored in the RAM (S394), and the process returns.

First, the level of the mirror down switch SWMRDN is checked (S320), the charge time measurement counter is counted up by 1 (S322), and the brake time soft counter is counted down by 1 (S324). When the level of the mirror down switch SWMRDN is the same level five times continuously, it is determined that the edge is switched, and “1” is substituted for the number of edges of the mirror down switch SWMRDN.
Like the mirror up switch SWMRUP, the mirror down switch SWMRDN in this embodiment is composed of a brush interlocking with the rotation of the mirror motor 33, and a code plate having a conducting portion and a non-conducting portion in sliding contact with the brush. When the mirror 37 is at the observation position, the mirror 37 is rotated from the observation position to the imaging position direction. When the mirror 37 is rotated toward the imaging position, the high level is maintained and the high level is maintained. Further, the mirror 37 swings from the imaging position to the observation position direction. When the observation position is reached, the low level is reached. Further, once the high level is reached, the low level is reached and the low level state is maintained.

"Mirror motor state 0 before PWM drive time has elapsed"
It is checked whether the mirror motor state is “0” (S326). If the mirror motor state is “0” (S326; Y), the PMW drive duty is changed to one step and the ON time is longer (S328). Then, it is checked whether or not the PWM drive time has ended (S330). If the PWM drive time has not ended (S330: N), S332 and S334 are skipped, and it is checked whether or not the first edge of the mirror down switch SWMRDN has been detected in the process of S320 (S336). If the first edge has not been detected (S336; N), S338, S340 and S342 are skipped, 200 μS has elapsed (S344), 200 μS has elapsed (S344; Y), and S318 is returned to. The processes after S320 are repeated. That is, it waits for the PWM drive time to end while changing the duty of PWM drive to the longer ON time every 200 μS.

“PWM drive time is complete, mirror motor state 1”
When the PWM drive time ends (S330; Y), the mirror motor 33 is driven in the DC forward rotation (S332), the mirror motor state is set to “1” (S334), and the first of the mirror down switch SWMRDN is processed in S320. Until the edge is detected (S336; N), the loop processing of S318 to S326; Y, S346; Y, S336 to S344, and S318 is repeated every 200 μS.

"SWMRDN first edge, primary brake, mirror motor state 2"
When the first edge of the mirror down switch SWMRDN is detected in the process of S320 (S336; Y), the primary brake is applied to the mirror motor 33 (S338), and the primary brake time for continuing the primary brake is set (S340). ), “2” is set in the mirror motor state (S342). Then, every 200 μS (S344; Y, S318 to S326; N, S346; N, S348; Y), it is checked whether or not the primary brake time has ended (S350). If the primary brake time has not ended (S350; Y), S352 and S354 are skipped, and it is checked whether or not the third edge of the mirror down switch SWMRDN is detected in the process of S320 (S356). ), If not (S356; N), return to S344 and check whether the primary braking time is finished every 200 μS (S344; Y, S318 to S326; N, S346; N, S348; Y) , S350). That is, it is checked whether or not the primary brake time is finished every 200 μS.

"Primary brake time elapsed, DC drive, mirror motor state 3"
When the primary brake time is over (S350; Y), the mirror motor is driven to rotate forward by DC (S352), and "3" is set to the mirror motor state (S354). Then, it is checked whether or not the number of edges of the mirror down switch SWMRDN is 3 (S356), and the loop processing is repeated until it becomes 3 times (S356; N, S344; Y, S318; N, S320 to S326). N, S346; N, S348; N, S364; Y, S356).

“SWMRDN edge number 3, PWM reverse brake, mirror motor state 4, D in FIG. 4”
“Before starting 5mS after braking”
When the number of edges of the mirror down switch SWMRDN becomes 3 (S356; Y), the PWM reverse brake control for the mirror motor 33 is started (S358), the reverse brake time is set, and the reverse brake state is identified in the mirror motor state. “4” is set (S362). Then, every time 200 μS elapses (S344; Y), the duty is changed in stages (S318; N, S320 to S326; N, S346; N, S348; N, S364; N, S366; Y, S368) ). In the step-by-step duty change processing in reverse brake processing, the PWM drive duty is changed step by step if it is within 5 mS after the start of reverse rotation, the ON time is changed to the longer one, and if within 5 mS before the start of reverse rotation, the ON time is shorter Change to That is, it is checked whether 5 mS has elapsed from the start of braking from the value of the mirror motor soft counter (S 370), and within 5 mS after the start of reverse rotation, the duty of PWM drive is increased by 1 for the longer ON time. Repeat the loop process to change the stage (S370; N, S374; N, S378; N, S344; Y, S318 to S326; N, S346; N, S348; N, S364; N, S366; Y, S368, S370) .

“After 5mS from the start of PWM reverse brake, up to 5mS before the end”
When 5 mS has elapsed after the start of the PWM reverse brake (S370; Y), the DC reverse brake is applied to the mirror motor 33 (S372). Then, in a state where the DC reverse brake is applied, wait for 5 ms before the end of the PWM reverse brake (S370; Y, S372, S374; N, S378; N, S344; Y, S318; N to S326; N, S346; N, S348; N, S364; N, S366; Y, S368, S370; Y, S372).

"Within 5mS before PWM reverse brake finish, PWM reverse brake"
When it is within 5 ms before the end of the PWM reverse brake (S374; Y), the PWM reverse brake is applied to the mirror motor 33 (S376). The PWM reverse rotation brake here repeats a loop process in which the duty is gradually decreased from the DC reverse rotation driving, that is, the duty is changed by one step so that the ON time becomes shorter (S374; Y, S376, S378; N, S344; Y, S318; N to S326; N, S346; N, S348; N, S364; N, S366; Y, S368, S370; N, S374).

"After reverse brake time, secondary brake, mirror motor state 5"
When the PWM reverse brake time ends (S378; Y), the secondary brake is applied to the mirror motor 33 (S380). The secondary brake is a short brake that short-circuits the input terminal of the mirror motor 33. Then, the secondary brake time is read from the EEPROM and set (S382), and "5" for identifying the state where the secondary brake is applied is set in the mirror motor state (S384).

  When “5” is set in the mirror motor state, a loop process for checking whether or not the secondary brake time is finished every 200 μs is repeated (S344; Y, S318; N to S326; N, S346; N, S348). N, S364; N, S366; N, S386; N, S344). Then, when the secondary brake time ends (S386; Y), the secondary brake is released (S388), that is, the input terminal of the mirror motor 33 is opened, and the mirror motor stop flag is set to “1”. After (S390), the process proceeds to S344, and after 200 μS has elapsed (S344; Y), the process returns to S318.

"Secondary brake time end, mechanical charge end, mirror motor stop flag 1"
When “1” is set in the mirror motor stop flag, the process proceeds from S318; Y to S392, and the end of the mechanical charge is transmitted to the DSP 15 by CPU-DSP communication (S392), and the mirror down time measurement is completed and measured. The time is stored in the RAM (S394), and the process returns. As is well known by the above mechanical charging process, the mirror is lowered to the observation position, the front curtain and the rear curtain move to the shooting standby state, and the front curtain and the rear curtain drive spring are charged.

1 is a block diagram showing an embodiment of a circuit configuration of a digital single lens reflex camera to which the present invention is applied. It is a figure which cuts and shows the principal part of the digital single-lens reflex camera to which this invention is applied along the optical axis. It is a figure which shows the timing chart at the time of release of the digital single-lens reflex camera. It is a figure which shows the detailed timing chart of the mirror up / down process part in the same timing chart, Comprising: (1) is a timing chart from mirror up to mirror down, (2) is a timing chart of PWM control at the time of mirror motor starting (3) is a diagram showing a timing chart of the PWM reverse brake. It is a figure which shows the flowchart regarding the main operation | movement of the digital single-lens reflex camera. It is a figure which shows the flowchart regarding the main operation | movement of the digital single-lens reflex camera. It is a figure which shows the flowchart regarding the mirror up process of the digital single-lens reflex camera. It is a figure which shows the flowchart regarding the mirror up process of the digital single-lens reflex camera. It is a figure which shows the flowchart regarding the mirror up process of the digital single-lens reflex camera. It is a figure which shows the flowchart regarding the mechanical charge (mirror down process) of the digital single-lens reflex camera. It is a figure which shows the flowchart regarding the mechanical charge (mirror down process) of the digital single-lens reflex camera. It is a figure which shows the flowchart regarding the mechanical charge (mirror down process) of the digital single-lens reflex camera.

Explanation of symbols

11 CPU
13 DPU
15 DSP
17 Battery 19 Power supply circuit 20 External strobe 21 Built-in strobe 23 Mode dial 25 Various switches 29 AFIC
33 Mirror motor 34 Mirror drive mechanism 35 Mirror detection switch 37 Mirror 38 Sub mirror 39 AF motor driver 41 AF motor 43 AF control photo interrupter 45 Split photometry IC
47 EEPROM
49 Shutter 51 External display LCD
51a LED for illumination
53 LCD in the viewfinder
53a LED for illumination
55 CCD image sensor 59 Av dial switch 61 Tv dial switch 63 Switch 65 Shutter switch 100 Shooting lens ESMg1 Shutter (front curtain) Magnet ESMg2 Shutter (rear curtain) Magnet SWM Main switch (Power switch)
SWS Metering switch SWR Release switch SWM UP Mirror up switch SWMRDN Mirror down switch

Claims (7)

A method of driving a motor mounted on a digital camera,
A method of driving a motor for a digital camera, characterized in that when the motor is started, the duty ratio is changed largely stepwise after starting energization by PWM control with a small duty ratio. In a digital camera including a mirror that moves a subject light incident from a photographing lens to an observation position that reflects the light in the direction of the optical viewfinder and an imaging position that allows incidence to the imaging unit, the mirror is moved from the observation position to the imaging position. A motor driving method for moving the imaging position to the observation position,
A method of driving a motor for a digital camera, characterized in that when the motor is started, the duty ratio is changed largely stepwise after starting energization by PWM control with a small duty ratio. 3. The motor driving method for a digital camera according to claim 1, wherein when a predetermined time elapses after energization of the motor is started by PWM control with a small duty ratio, the DC motor is energized. 3. The motor driving method for a digital camera according to claim 1 or 2, wherein the duty ratio is changed in a stepwise manner until the DC energization is started after the energization is started by the PWM control with the small duty ratio. 5. A motor driving method for a digital camera according to claim 3, wherein when the motor being driven is stopped, a reverse brake for PWM control is applied before starting and ending. 6. The motor drive method for a digital camera according to claim 5, wherein the reverse brake by the PWM control changes the duty ratio stepwise from small to large during the start of reverse brake application, and the duty ratio before the reverse brake ends. A method for driving a digital camera motor that gradually changes from large to small. 7. The motor driving method for a digital camera according to claim 6, wherein the reverse brake applies a reverse braking by direct current during a predetermined period when the reverse braking starts and during a predetermined period before the reverse braking ends.

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