JP2013148653A - Optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately drive a diaphragm to a targeted diaphragm position.SOLUTION: A lens microcomputer 23 controlling a stepping motor 25 gives a coil 253 of the stepping motor a periodic driving signal including an initial signal moving a magnet rotor 251 to an initial position corresponding to an opening position of a diaphragm 22. When the diaphragm is not at the opening position thereof after the initial signal was given, the lens microcomputer changes the driving signal so as to move the rotor of the stepping motor by the number of steps of an absolute value of a value deducting the number of steps of one period of the driving signal from the number of steps corresponding to an amount of driving from a reference position of the diaphragm to a targeted position thereof. Further, when the number of steps corresponding to the amount of driving is smaller than the number of steps of the one period of the driving signal, the lens microcomputer reverses a rotor driving direction.

Description

  The present invention relates to an optical apparatus.

  In Patent Document 1, when driving a diaphragm blade of a step motor (stepping motor), if a signal notifying that the diaphragm blade has a specific aperture value is not output, low speed driving is performed to move the rotor to the initial position. A method of returning to step S1 and then reducing the driving speed is disclosed. Patent Document 2 discloses a method of calculating a drive amount for moving to a target aperture position based on an open position when the position sensor detects an aperture open position, and driving by this drive amount.

Japanese Patent Laid-Open No. 2-105121 JP 2009-175622 A

  A drive signal is applied to the coil of the step motor, and this drive signal is a periodic drive signal including an initial signal for moving the rotor to an initial position. This initial position is usually the opening position of the diaphragm. However, the rotor tends to fluctuate when the coil is turned off. As a result, even if an initial signal is subsequently applied by energization to move the roller to the initial position, the rotor may jump to a position shifted by one cycle from the initial position (jump phenomenon). After that, if the rotor is moved by the drive amount from the aperture opening position to the target position, the initial position is shifted by one cycle, resulting in the drive position being shifted from the target position by one cycle, and the aperture positioning accuracy There was a problem that decreased. The above two publications do not consider this jump phenomenon at all.

  Accordingly, an object of the present invention is to provide an optical apparatus that can accurately drive the aperture to a target position.

  The optical apparatus of the present invention has detection means for detecting whether or not an aperture through which light passes is variable, and a diaphragm control means for controlling a step motor that drives the diaphragm, The aperture control means gives a periodic drive signal including an initial signal for moving the rotor of the step motor to an initial position corresponding to the reference position of the aperture to the coil of the step motor, and the aperture control means A step corresponding to a driving amount of the diaphragm from the reference position to a target position when the detecting means detects that the diaphragm is not in the reference position after applying the initial signal to the coil of the step motor; The drive signal is modified so that the rotor of the step motor is moved by the absolute number of steps obtained by subtracting the number of steps for one cycle of the drive signal. Characterized in that the number of steps corresponding to the driving amount to reverse the driving direction of the rotor is smaller than the number of steps of one cycle of the drive signal.

  ADVANTAGE OF THE INVENTION According to this invention, the optical apparatus which can drive an aperture_diaphragm | restriction to a target position accurately can be provided.

It is a block diagram of the camera system of this embodiment. FIG. 2 is a perspective view of a diaphragm unit including a diaphragm and a diaphragm drive unit illustrated in FIG. 1. FIG. 3 is a principle diagram of a step motor as the diaphragm drive unit shown in FIG. 2. FIG. 4 shows drive waveforms of an A-phase coil and a B-phase coil in 1-2 phase excitation of the step motor shown in FIG. 3. It is a figure explaining an aperture unit. 3 is a flowchart for explaining processing when the lens microcomputer shown in FIG. 1 receives an aperture drive instruction. It is a flowchart which shows the detail of S308 of FIG. It is a flowchart which shows the detail of S308 of FIG.

  FIG. 1 is a block diagram of the camera system (optical apparatus) of this embodiment. The camera system includes a camera body (imaging device, optical device) 10 and an interchangeable lens (optical device) 20 that is detachably attached to the camera body 10.

  The camera body 10 and the interchangeable lens 20 are mechanically coupled by a mount (not shown) and are communicably connected via a connector (not shown). Through the communication, the camera body 10 and the interchangeable lens 20 can exchange information such as their identification numbers, specifications, and functions. In addition, power is supplied from the camera body 10 to the interchangeable lens 20 via the connector.

  The camera body 10 includes a camera microcomputer 11, a photometric sensor 12, an image sensor 14, an image processing circuit 16, and various switches 18.

  The camera microcomputer 11 controls each part of the camera body 10 and communicates with the lens microcomputer 23 of the interchangeable lens 20. The photometric sensor 12 measures subject brightness. Since the photometric sensor 12 has a known logarithmic compression circuit, its output is logarithmically compressed. The image sensor 14 photoelectrically converts an optical image formed by the imaging optical system of the interchangeable lens 20. The image processing circuit 16 processes the image signal output from the image sensor 14 and sends it to a memory (not shown) or the camera microcomputer 11. The various switches 18 set power on / off, shooting modes (still image shooting mode, moving image shooting mode), playback mode, erase mode, PC connection mode, and the like.

  The interchangeable lens 20 includes a photographing optical system, a lens microcomputer 23, and a step motor (stepping motor) 25 that is an aperture drive unit. The imaging optical system forms an optical image of an object, and includes a lens group 21 such as a focus lens, a zoom lens, and a camera shake correction lens, a diaphragm 22 that adjusts the amount of light incident on the image sensor 14, and the like. In FIG. The lens microcomputer 23 controls each part of the interchangeable lens 20 and communicates with the camera microcomputer 11. The lens driving unit 24 drives the lens group.

  FIG. 2 is a perspective view of a diaphragm unit including a diaphragm 22 having a variable aperture through which light passes and a step motor 25 that drives a diaphragm blade that forms the aperture of the diaphragm 22 to change the aperture diameter.

  The step motor 25 is driven by a drive amount based on the measurement result of the photometric sensor 12. The step motor has a magnet rotor 251, a stator 252, and a coil 253. A drive signal is applied to the coil 253 of the step motor 25. This drive signal is a periodic drive signal including an initial signal for moving the magnet rotor 251 to the initial position.

  The aperture 22 includes a presser plate 221, a cam plate 222, a tapped hole light shielding plate 225 and a rotating ring (not shown), an aperture opening detection switch 226, an aperture blade, and the like.

  The rotating ring receives a rotational force from the step motor 25 and opens and closes the aperture blade according to a cam (not shown) formed on the cam plate 222. The aperture opening detection switch 226 is composed of, for example, a photo interrupter, and is turned on / off when the light shielding plate 225 passes between the aperture opening detection switches 226, and detects whether the aperture 22 is opened or closed. It is. However, it is sufficient that the detecting means can widely detect whether or not the diaphragm 22 is at the reference position, and the reference position is not limited to the open position.

  The diaphragm 22 is attached to the lens barrel by the tap hole 221a of the holding plate 221. The cam plate 222 rotates with respect to the holding plate 221 and a rotating ring (not shown), so that the diaphragm blades (not shown) Opens and closes and functions as a diaphragm aperture correction mechanism. Normally, the aperture diameter correction mechanism is performed in conjunction with a zoom operation by a cam on the lens barrel side (not shown) with a roller attached to the tap hole 222a of the cam plate 222.

  FIG. 3 is a principle diagram of the step motor. 252a is an A-phase stator, 253a is an A-phase coil wound around the A-phase stator, 252b is a B-phase stator, 253b is a B-phase coil wound around the B-phase stator, and 251 is a magnet rotor. N pole and S pole are magnetized. The pole of each stator 252 is switched according to the direction of energization of each coil 253.

  FIG. 4 shows drive waveforms of the A-phase coil and the B-phase coil in 1-2 phase excitation, which is an example of the drive signal. (A) shows an energized voltage, and (b) shows a drive current. The 1-2 phase excitation has eight energization patterns. In FIG. 4A, the energization voltage pattern is changed in the right direction to move in the narrowing direction, and the energization voltage pattern is changed in the left direction to move in the open direction.

  The step motor is configured to match the predetermined pattern of 1-2 phase excitation at the aperture opening position (reference position), but another aperture position may be set as the reference position. For example, the initial signal for moving the magnet rotor 251 to the initial position corresponding to the aperture opening position is the energization pattern m1 shown in FIG. 4A, and the aperture value manipulated variable by 1-step of 1-2 phase excitation is 1/8 step. And The drive speed of the diaphragm 22 can be adjusted by adjusting the change time of the 1-2 phase excitation pattern.

  FIG. 5A is a schematic plan view of the diaphragm 22, and AP is an opening. The open aperture value of the aperture 22 is determined by the inner diameter dimension (open diameter) of the disc-shaped presser plate 221 mechanically fixed. The aperture value is determined by taking in and out a plurality of plates called aperture blades 223 by rotating the step motor. Normally, the opening position is the initial position where the diaphragm blade 223 does not protrude beyond the inner diameter of the presser plate 221. 5A is the difference between the position of the diaphragm blade 223 at the initial position of the step motor and the position where the position of the diaphragm blade 223 is just the inner diameter of the holding plate 221 (for four steps). is there.

  To reduce the aperture by 2 steps from the fully open position, energize the energization pattern m1, and then change the 1-2 phase excitation pattern by 20 steps including the run-up section amount (4 steps) and the 2-step equivalent amount (16 steps). Then, the step motor is driven.

  FIG. 5B is a diagram for explaining the problem of the conventional jump phenomenon, and the output of the open detection switch 226 is indicated by H and L. FIG. It is at the H level near the initial position (open position), and at the small aperture side from the open diameter position. When the switch 18 is operated and the power supply to the coil 253 is turned off, the magnet rotor 251 is likely to fluctuate. As a result, even if the switch 18 is subsequently operated and an initial signal is given by energization to move the roller to the initial position, the rotor may jump to a position shifted by one cycle from the initial position. . In FIG. 5 (b), when there is a jump phenomenon, the magnet rotor 251 does not move to m1, but jumps to m1 ′, which is 8 steps away from the m1, and the phenomenon increases as the number of magnetic poles of the magnet rotor 251 increases. Become prominent.

  When a shutter button (not shown) is operated and a shooting preparation operation is performed, the camera microcomputer 11 calculates an exposure value according to the measurement result of the photometric sensor 12 and the ISO sensitivity. Command to reduce the aperture value to. After shooting, the camera microcomputer 11 instructs the lens microcomputer 23 to open the aperture 22. At this time, the lens microcomputer 23 drives the diaphragm 22 via the step motor 25 according to the diaphragm driving amount or the diaphragm driving speed instructed from the camera microcomputer 11.

  FIG. 6 is a flowchart for explaining processing when the lens microcomputer 23 configured as a microcomputer receives an aperture driving instruction. In FIG. 6, “S” is an abbreviation for “step”, and the method shown in FIG. 6 can be implemented as a program for causing a computer (lens microcomputer 23) to realize the function of each step. Note that the camera microcomputer 11 may perform the flow of FIG. Therefore, the lens microcomputer 23 or the camera microcomputer 11 functions as an aperture control unit that controls the driving of the aperture 22 by the step motor 25 based on the detection result of the aperture opening detection switch 226 described above. In addition, the lens microcomputer 23 and the camera microcomputer 11 have time measuring means for measuring time set using a crystal clock (not shown).

  First, when the lens microcomputer 23 receives an aperture drive instruction and drive data, it determines whether it is a small aperture drive or an open drive (S301). In the case of driving to the open side (Y in S301), the lens microcomputer 23 determines whether the aperture is open or closed based on the output of the aperture open detection switch 226 (S302), and the aperture 22 is opened. In the case of (Y in S302), the process is terminated. On the other hand, when the diaphragm 22 is narrowed down (N in S302), the lens microcomputer 23 uses the received drive amount as the drive amount, and starts driving toward the open side at the previously received aperture drive speed (S303). Thereafter, in the opening drive process (not shown), the step motor is driven until the received drive amount becomes equal to the control drive amount, and the drive is terminated. Further, during the driving to the open side, the output of the aperture opening detection switch 226 is detected, and if it is determined to be in the open position, the drive is driven to the initial position of the step motor regardless of the drive amount, and the drive is terminated.

  On the other hand, when the lens microcomputer 23 determines that the drive is to the small aperture side (N in S301), it determines whether the aperture 22 is open or closed based on the output of the aperture open detection switch 226 (S304). If the aperture 22 is narrowed (N in S304), the lens microcomputer 23 sets the received drive amount as the drive amount (S305), and starts driving toward the small aperture side based on the previously received aperture drive speed. (S306). Thereafter, in the narrowing-down driving process (not shown), the step motor is driven until the received drive amount becomes equal to the control drive amount, and the drive is terminated. When the maximum aperture position that can be driven is reached during driving toward the small aperture side, the driving of the step motor is terminated regardless of the drive amount.

  On the other hand, when the aperture 22 is open (Y in S304), the lens microcomputer 23 sets the driving amount by adding the run-up driving amount to the received driving amount (S307), and sets the small aperture according to the previously received aperture driving speed. Drive to the side is started (S308). Thereafter, in the narrowing-down drive process described later, the step motor is driven until the received drive amount becomes equal to the control drive amount, and the drive ends. If the maximum aperture position that can be driven is reached during driving toward the small aperture side, the driving of the step motor is terminated regardless of the drive amount.

  7 and 8 are flowcharts showing details of the narrowing drive 2 (S308). S308 comprises two types of initial processing and predetermined time interval processing after the initial processing. FIG. 7 shows the initial processing, and FIG. 8 shows the predetermined time interval processing.

  First, the initial process will be described with reference to FIG. The lens microcomputer 23 sets the drive amount set in S307 to STEP_V and clears STEP_C to 0 (S401). Next, since the lens microcomputer 23 is driven from the open position, energization of the step motor is started by the energization pattern at the open position (m1 described in FIG. 4A) (S402). Next, the lens microcomputer 23 sets a time until execution of the predetermined time interval process, and ends the process (S403). Here, the time measured by the time measuring means is a fixed value, and the aperture driving process is executed after 1 ms. However, the time to be set may not be a fixed value. For example, time data corresponding to STEP_C may be provided in advance and variably set according to the value of STEP_C.

  Next, the predetermined time interval processing after the initial processing will be described with reference to FIG. The lens microcomputer 23 determines whether or not STEP_C is 0 (S501). If it is 0 (Y in S501), the lens microcomputer 23 determines whether it is open because it is a process immediately after initial energization (S502). If it is detected at this timing that the aperture is full (Y in S502), it can be determined that the jump phenomenon has not occurred, and normal processing (processing after S507) is performed. However, if it is detected at this timing that the aperture is not fully open (N in S502), it is determined that a jump phenomenon has occurred, and a jump phenomenon response process (process after S503) is performed.

  If the lens microcomputer 23 determines that it is not open (N in S502), it has moved to the 8-step aperture side due to the jump phenomenon, so STEP_C is set to 8 (S503), and it is determined whether STEP_V is less than 8 or not. (S504). If STEP_V is not less than 8 (N in S504), since the 1-2 phase excitation is assumed in this embodiment, the target position is located on the small aperture side even if the jump phenomenon occurs. Therefore, the lens microcomputer 23 subtracts the drive amount 8 corresponding to the jump from the drive amount STEP_V and sets it to STEP_V (S505). On the other hand, if STEP_V is larger than 8 (Y in S504), it means that the target position is passed when the jump phenomenon occurs, and the target position is located on the open side. Therefore, the lens microcomputer 23 subtracts the drive amount STEP_V from the drive amount 8 corresponding to the jump, sets it to STEP_V, and changes to the open direction drive (S506). From S506 and S506, the lens microcomputer 23 moves the rotor by the number of steps of an absolute value obtained by subtracting the number of steps of one cycle of the drive signal from the number of steps corresponding to the drive amount from the aperture opening position to the target position. Thus, the drive signal is corrected. In S506, the lens 23 reverses the driving direction of the magnet rotor 251 if the number of steps corresponding to the target driving amount is smaller than the number of steps corresponding to one cycle of the driving signal.

  If STEP_C is not 0 (N in S501) or is open (Y in S502), the lens microcomputer 23 determines whether STEP_C matches STEP_V after S505 or S506 (S507). If they coincide with each other (Y in S507), it is determined that the target position has been reached, and the driving is ended while the energization is turned off or held (S511).

  On the other hand, if STEP_C does not match STEP_V (N in S507), the lens microcomputer 23 determines that the target position has not been reached, and increments STEP_C by 1 for driving in the narrowing direction, and STEP_C for driving in the opening direction. Decrement by 1 (S508). Then, the lens microcomputer 23 changes the energization pattern to the right as shown in FIG. 4A in the narrowing direction drive, and to the left as shown in FIG. 4A in the open direction drive (S509). Next, the lens microcomputer 23 sets a time until execution of the predetermined time interval process, and ends (S510). Here, the set time is a fixed value, and it is assumed that the aperture driving process is executed after 1 ms. However, the time to be set may not be a fixed value. For example, time data corresponding to STEP_C may be provided in advance and variably set according to the value of STEP_C.

  As described above, in this embodiment, at the timing after the initial energization, it is detected whether or not the aperture is fully open. If the aperture is not fully open, it is determined that a jump has occurred and the target drive amount is corrected and corrected. The stepping motor is driven with the driven amount. Therefore, even when a jump phenomenon occurs, the diaphragm can be accurately driven to the target position.

  As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

  The aperture control device can be applied to an imaging device such as an interchangeable lens or a camera.

DESCRIPTION OF SYMBOLS 10 ... Camera body, 11 ... Camera microcomputer (aperture control means), 20 ... Interchangeable lens, 22 ... Aperture, 23 ... Lens microcomputer (aperture control means), 25 ... Step motor, 251 ... Magnet rotor, 253 ... Coil, AP ... Opening

Claims (5)

Detecting means for detecting whether or not an aperture through which light passes is variable at a reference position;
Diaphragm control means for controlling a step motor for driving the diaphragm,
The diaphragm control means provides a periodic drive signal including an initial signal for moving the rotor of the step motor to an initial position corresponding to the reference position of the diaphragm to the coil of the step motor;
The diaphragm control means drives the diaphragm from the reference position to a target position when the detection means detects that the diaphragm is not in the reference position after applying the initial signal to the coil of the step motor. The drive signal is corrected so that the rotor of the step motor is moved by an absolute number of steps obtained by subtracting the number of steps of one cycle of the drive signal corresponding to the amount, An optical apparatus characterized in that the driving direction of the rotor is reversed if the corresponding number of steps is smaller than the number of steps of one cycle of the drive signal.   The optical apparatus according to claim 1, wherein the reference position of the diaphragm is an open position. It further has a time measuring means for measuring the set time,
The aperture control means determines whether or not the aperture is at the reference position after the time measuring means counts the set time after the initial signal is given to the coil of the step motor. The optical apparatus according to claim 1.   4. The optical device according to claim 1, wherein the optical device includes an aperture lens, the detection unit, and the step motor, and is an interchangeable lens that is detachably attached to a camera body. 5. Optical equipment.   The optical apparatus according to any one of claims 1 to 3, wherein the optical apparatus is a camera system including a camera body and an interchangeable lens attached to the camera body.