JP2011123335A - Optical device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an optical device which allow a lens holding frame to be accurately stopped at a desired position in the direction of an optical axis while a difference between a control signal to a driving-force generating means and the actual drive of the lens holding frame, which is caused by backlash in a driving-force transmitting means, is reduced to reduce delay in drive when starting the lens holding frame. <P>SOLUTION: The optical device includes: a lens group movable relative to the direction of at least one optical axis in a photographing optical system having a plurality of lens groups; the lens holding frame holding the lens group movable relative to the direction of the optical axis; the driving force generating means for moving the lens holding frame; the driving-force transmitting means for transmitting a driving force, generated by the driving-force generating means, to the lens holding frame; a driving-force control means for controlling the drive of the driving-force generating means; a braking means for fixing the lens holding frame at any position in the direction of the optical axis; and a brake controlling means for controlling the braking means. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical device, and can perform high-precision drive control of a lens holding frame that moves in an optical axis direction. For example, a single-lens reflex camera, a compact camera, a surveillance camera, a TV camera, a liquid crystal projector, and an AF function It is suitable for binoculars.

  Conventionally, the lens holding frame is driven to change the focal length of the photographic lens by the photographer's operation (to perform zooming) or to focus on the subject (focus) according to the distance measurement result to the subject. The optical axis is moved by the means. As the movement at this time, there is known an optical apparatus configured to drive and control the lens holding frame in the optical axis direction using a driving force generating unit such as a motor and a driving force transmission unit such as a gear train. In such an optical apparatus, when it is desired to stop the lens holding frame at a desired position in the optical axis direction, even if the driving force generating means is stopped during the movement of the lens holding frame, the inertia or the driving force transmitting means The lens holding frame does not stop instantaneously due to this gap. In many cases, the lens holding frame may move beyond a desired position. Unless the lens holding frame is accurately positioned and stopped at a desired position in the optical axis direction, a focus shift occurs and a captured image deteriorates.

  2. Description of the Related Art Conventionally, cameras (optical devices) having a configuration for accurately positioning the position of a lens holding frame in the optical axis direction are known (Patent Documents 1 and 2). In the camera of Patent Document 1, a gap is formed between the moving frame and the guide member during movement of the moving frame that holds the lens, while the gap between the moving frame and the guide member is eliminated before the exposure operation (when photographing). I have to. Thus, a camera is disclosed in which the lens position (moving frame position) is accurately positioned to improve the photographing performance. In the camera with a zoom of Patent Document 2, when the movable member such as a lens is moved and then stopped, brake control is applied to the power of the movable member, and the brake means performs appropriate control according to the moving state of the movable member. Is disclosed.

JP-A-5-045551 Japanese Patent Laid-Open No. 9-230212

  In the configuration of the conventional optical apparatus, when the lens holding frame is positioned and stopped, a control signal to the driving force generating means (motor) generated by play in the driving force transmitting means and an actual driving deviation of the lens holding frame are reduced. Is difficult. In particular, with the configurations disclosed in Patent Documents 1 and 2, it is difficult to reduce the drive delay at the start of driving of the lens holding frame and the positional deviation from a predetermined position in the optical axis direction at the stop.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an optical device that can reduce a deviation between a control signal to a driving force generating means and an actual driving of a lens holding frame caused by play in the driving force transmitting means. It is another object of the present invention to provide an optical device that can reduce the drive delay at the time of starting the lens holding frame and can accurately stop the lens holding frame at a desired position in the optical axis direction.

  An optical device according to the present invention includes a lens group that holds at least one lens group that is relatively movable in the optical axis direction and a lens group that is relatively movable in the optical axis direction in a photographing optical system having a plurality of lens groups. Driving force generating means for moving the lens holding frame, driving force transmitting means for transmitting the driving force generated from the driving force generating means to the lens holding frame, and controlling driving of the driving force generating means Driving force control means, brake means for fixing the lens holding frame at an arbitrary position in the optical axis direction, and brake control means for controlling the brake means.

  According to the present invention, it is possible to obtain an optical apparatus capable of reducing a deviation between a control signal to the driving force generating means and an actual driving of the lens holding frame caused by play in the driving force transmitting means. As a result, an optical device can be obtained that can reduce the drive delay at the start of the lens holding frame and can accurately stop the lens holding frame at a desired position in the optical axis direction.

1 is a block diagram illustrating a configuration of an optical device according to a first embodiment of the present invention. 5 is a flowchart for explaining the processing operation of the optical apparatus according to the first embodiment of the present invention. 5 is a flowchart for explaining a processing operation at the start of the photographing lens according to the first embodiment of the present invention. 5 is a flowchart for explaining a processing operation during driving of the taking lens according to the first embodiment of the present invention. 6 is a flowchart for explaining a processing operation when the photographic lens is stopped in Embodiment 1 of the present invention. FIG. 3 is a cross-sectional view seen from the top surface of the photographic lens in Example 1 of the present invention. 1 is a developed perspective view of a photographic lens in Embodiment 1 of the present invention. Sectional drawing seen from the upper surface and front of the brake means in Example 1 of this invention. 9 is a flowchart for explaining a processing operation of a photographic lens in Embodiment 2 of the present invention.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. The optical apparatus according to the present invention includes a photographing optical system having a plurality of lens groups such as a focus lens 11 and a zoom lens 13 and at least one lens group (focus lens group) 11 that can be relatively moved in the optical axis direction. And a lens holding frame (focus lens holding frame) 12. Driving force generating means (lens driving motor) 23 using a DC motor or the like for moving the lens holding frame 12, and a gear train or the like for transmitting the driving force generated from the driving force generating means 23 to the lens holding frame 12. A driving force transmission means (deceleration unit) 24 is provided. Furthermore, it has driving force control means (lens driving circuit) 22 for controlling driving of the driving force generating means. Brake means (brake unit) 28 for fixing the lens holding frame 12 at an arbitrary position in the optical axis direction, and brake control means (brake drive circuit) 27 for controlling driving of the brake means 28 are provided.

  When the lens holding frame (focus lens holding frame) 12 is driven in the optical axis direction by the driving force control means (lens driving circuit) 23, the following is performed. Prior to the generation of the driving force of the driving force generating means (lens driving motor) 23 for moving the lens holding frame 12, the brake control means 27 first drives the brake means 28 to fix the lens holding frame (non-moving). ). Thereafter, after a predetermined time has elapsed from the start of driving of the driving force generating means 23, the driving of the brake means 28 is released and the driving of the lens holding frame 12 is started. At this time, a predetermined time from the start of driving of the driving force generating means (lens driving motor) 23 to the release of driving of the brake means 28 is set as follows. For example, a predetermined time may be set depending on whether the current movement direction is the same direction or the reverse direction with respect to the previous movement direction of the lens holding frame 12, and the movement direction is not determined. In addition, a predetermined time for obtaining a sufficient effect may be set regardless of the moving direction.

  In addition, the optical apparatus may have drive detection means (pulse generator) 29 for detecting the drive state of the drive force generation means (lens drive motor) 23 or the drive force transmission means (deceleration unit) 24. . At this time, the brake control means (brake control circuit) 27 confirms the drive state detected by the drive detection means, for example, the stop of the drive force generation means (lens drive motor) 23 or the drive force transmission means (deceleration unit) 24. Thereafter, the driving of the brake means may be released and the driving of the lens holding frame 12 may be started.

  Next, when the lens holding frame (focus lens holding frame) 12 moving in the optical axis direction by the driving force from the driving force generating means (lens driving motor) 23 is stopped and fixed, the following is performed. . The brake control means (brake control circuit) 27 drives the brake means (brake unit) 28 before the driving force from the driving force generation means (lens driving motor) 23 for moving the lens holding frame 12 disappears. Thereby, the lens holding frame 12 is fixed at a predetermined position in the optical axis direction. Thereafter, energization to the driving force generating means 23 is stopped.

[Example 1]
FIG. 1 is a principal block diagram illustrating a configuration of an optical apparatus (camera system) according to a first embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a camera (camera body), and 2 denotes a photographing lens (interchangeable lens) that can be attached to and detached from the camera 1. In the camera 1, 3 is an electric circuit. The electric circuit 3 includes a photometric unit 4 for measuring the amount of light that has passed through the photographic optical system of the photographic lens 2, a focus detection unit 5 for detecting the focus adjustment state of the photographic optical system, and a photographic film. A shutter 6 for controlling the exposure time is provided. Further, a feeding charge system 7 for winding and rewinding the film, a camera CPU 8 for controlling various controls in the camera 1, and a communication circuit 9 for performing serial communication with the photographing lens 2 are also provided. A power supply 10 is provided in the camera 1, and power is supplied from the power supply 10 to the electric circuit 3 and the photographing lens 2.

  In the photographic lens 2, reference numeral 11 denotes a focus lens, and reference numeral 13 denotes a zoom (exchange) lens, which are held by a focus lens holding frame 12 and a zoom lens holding frame 14 that hold them. Reference numeral 15 denotes an aperture unit. The photographing lens 2 has a photographing optical system including the focus lens 11, the zoom lens 13, the diaphragm unit 15, and the like. Reference numeral 16 denotes a zoom brush that slides on a resistor (not shown) as the zoom lens holding frame 14 moves in order to detect the position of the zoom lens 13 in the optical axis direction. A signal having a voltage value corresponding to the position in the optical axis direction is output. Reference numeral 17 denotes a focus brush that slides on a resistor (not shown) as the focus lens holding frame 12 moves in order to detect the position of the focus lens 11 in the optical axis direction. A signal having a voltage value corresponding to the position of is output.

  Reference numeral 18 denotes an A / M switch for switching between auto focus (AF) and manual focus (MF). Reference numeral 19 denotes an electric circuit in the photographic lens 2. The electrical circuit 19 includes a communication circuit 20 for performing serial communication with the camera 1, an in-lens CPU 21 that controls the inside of the photographing lens 2, a lens driving circuit 22, an aperture driving circuit 25, a brake driving circuit 27, and the like. Is provided. The lens driving circuit (driving force control means) 22 controls the driving of the lens driving motor (driving force generating means) 23 in accordance with a control signal from the lens CPU 21, and focuses through the deceleration unit (driving force transmitting means) 24. The lens holding frame 12 is driven. The aperture driving circuit 25 controls the driving of the aperture driving motor 26 according to the control signal from the lens CPU 21 and drives the aperture unit 15. The brake drive circuit (brake control means) 27 performs drive control of the brake unit (brake means) 28 in accordance with a control signal from the lens CPU 21, and moves the focus lens holding frame 12 in the optical axis direction with respect to the other lens groups. Fix at any position.

  Further, the photographing lens 2 is provided with a pulse generator (drive detection means) 29 that generates a pulse signal as the focus lens holding frame 12 moves. The pulse generator 29 has a pulse plate in which a plurality of slit portions are formed in a disk that rotates as the focus lens holding frame 12 moves. Furthermore, it has a photo interrupter which detects the light which permeate | transmits a slit part by this pulse plate rotating, and generate | occur | produces a pulse signal.

  Next, the automatic focus adjustment processing operation according to the first embodiment of the present invention will be described with reference to the flowcharts of FIGS. FIG. 2 is a flowchart of processing on the camera 1 side (mainly the camera CPU 8) in the camera system of the present embodiment.

“Step 101” When an imaging preparation switch (not shown) is turned on, the automatic focus adjustment processing operation in the camera CPU 8 starts.
“Step 102” The camera CPU 8 outputs a signal for causing the focus detection unit 5 to perform focus detection.
“Step 103” The camera CPU 8 calculates the defocus amount of the photographing optical system from the focus detection result obtained in step 102.
“Step 104” The camera CPU 8 determines whether or not the defocus amount obtained in step 103 is within the in-focus range. If it is within the focus range, the process proceeds to step 109, and if it is outside the focus range, the process proceeds to step 105. Here, the in-focus range is a range set based on the fact that the amount of focus shift is within the allowable circle of confusion.

“Step 105” Since it is determined that the focus range is out of step 104, the lens drive amount to drive the focus lens holding frame 12 that holds the focus lens 11 to the focus position based on the defocus amount obtained in step 103. Is calculated. This lens driving amount is calculated as the amount of the pulse signal generated by the pulse generator 29. The lens driving amount is stored in a memory in the camera CPU 8.
“Step 106” The camera CPU 8 is configured to drive the focus lens 11 with the lens driving amount calculated in step 105 by communication via the communication circuit 9 on the camera 1 side and the communication circuit 20 on the lens 2 side. 2 outputs a focus drive command.
“Step 107” The camera CPU 8 receives the status signal of the photographing lens 2 via the communication circuits 9 and 20. Through this lens status communication, the driving state of the focus lens holding frame 12 in the photographing lens 2 is communicated to the camera 1 side.

“Step 108” The camera CPU 8 determines whether or not the focus lens holding frame 12 is in a driving state based on the lens status communication performed in Step 107. If the focus lens holding frame 12 is being driven, the process returns to Step 107.
“Step 109” Since it is determined in step 104 that it is within the focusing range, the camera CPU 8 performs focusing processing.
“Step 110” The processing on the camera side until focusing is completed.

  In this way, on the camera 1 side, the focus detection and the driving of the focus lens 11 are repeatedly performed until the amount of focus deviation of the photographing optical system becomes a predetermined amount or less.

  3 to 5 are flowcharts of processing on the photographing lens 2 side (mainly the lens CPU 21). FIG. 3 shows a processing operation when the photographing lens 2 is started, FIG. 4 shows a processing operation while the photographing lens is being driven, and FIG. 5 shows a processing operation when the photographing lens is stopped. In addition, the part which attached | subjected the same encircled number in FIGS. 3-5 shows connecting with each other. A processing operation at the time of starting the photographing lens 2 of FIG. 3 will be described.

“Step 111” The lens CPU 21 receives a focus drive command from the camera 1 side through communication at step 106 in FIG.
“Step 112” The lens CPU 21 sets a focus driving flag, which is one of information transmitted to the camera 1 in the lens status communication in step 107 of FIG. 2 described above. While this flag is set, the camera 1 determines that the focus lens holding frame 12 is being driven.
“Step 113” The lens CPU 21 stores the focus drive amount transmitted from the camera 1 side in step 111 in a memory in the lens CPU 21.
“Step 114” The lens CPU 21 includes a pulse width measurement timer for measuring the time from the rise to the fall of the pulse signal output from the pulse generator 29 and the time from the fall to the rise of the next pulse signal. Yes. That is, the time during which the output signal from the pulse generator 29 does not change is measured.

“Step 115” The lens CPU 21 outputs a control signal to the brake drive circuit 27, starts energization of the brake unit 28, and starts driving. That is, the brake unit 28 is driven to make the focus lens holding frame 12 immovable.
“Step 116” The lens CPU 21 outputs a control signal to the lens drive control circuit 22 and starts energization to the lens drive motor 23. At this time, the focus lens holding frame 12 is driven, but since the brake is applied by the brake unit 28, the focus lens holding frame 12 is not driven immediately.
“Step 117” The lens CPU 21 determines whether the next lens driving direction is the same as the previous driving direction. If the directions are the same, the process proceeds to step 118, and otherwise, the process proceeds to step 119.
“Step 118” The lens CPU 21 determines whether or not a predetermined time during forward rotation has elapsed. If the predetermined time has not elapsed, the state of step 117 is maintained, and if the predetermined time has elapsed, the process proceeds to step 120.

“Step 119” The lens CPU 21 determines whether a predetermined time at the time of inversion has elapsed. If the predetermined time has not elapsed, the state of step 117 is maintained, and if the predetermined time has elapsed, the process proceeds to step 120.
“Step 120” The lens CPU 21 outputs a control signal to the brake drive circuit 27 when a predetermined time has elapsed during forward rotation or when a predetermined time has elapsed during reverse rotation, and energization of the brake unit 28 is terminated. As a result, the brake of the brake unit 28 is released and the focus lens holding frame 12 starts driving.

  In this way, on the photographic lens 2 side, after receiving the focus drive command from the camera 1 side, the brake unit 28 is driven before the focus lens 11 is driven, and the focus lens holding frame 12 is braked and fixed. Start driving the lens. Although the deceleration unit 24 tries to drive, the focus lens holding frame 12 cannot be moved by the brake unit 28, so the play in the deceleration unit 24 is clogged.

  Here, the lens CPU 21 determines whether or not the current lens driving direction is the same direction as the previous driving direction, and after a predetermined time has passed to allow sufficient rattling according to each driving direction, The driving of the unit 28 is finished and the driving of the brake unit 28 is released. Thereafter, the focus lens holding frame 12 is driven. Accordingly, the deceleration unit 24 starts driving the focus lens holding frame 12 from a state where there is no backlash. At this time, the predetermined time until the brake means is released may be different depending on whether it is the same as or opposite to the previous driving direction.

Processing operations during driving of the photographic lens 2 of FIG. 4 will be described.
“Step 121” The lens CPU 21 determines whether or not a pulse signal is input from the pulse generator 29. If a pulse signal is input, the process proceeds to step 122. If there is no input, the process returns to step 121.
“Step 122” Since the pulse signal is input in Step 121, the pulse count value (P _c ) indicating the current position of the focus lens holding frame 12 is changed. Therefore, the lens CPU 21 increases the pulse count value by the amount of change.
“Step 123” Since the pulse signal is input in step 121, the lens CPU 21 reads the pulse width indicating the current driving speed.
“Step 124” The lens CPU 21 determines whether or not the pulse count value P _c indicating the current position is smaller than _a predetermined acceleration pulse Pa. If it is smaller than the acceleration pulse, the process proceeds to step 125, and if it is greater than the acceleration pulse, the process proceeds to step 126. Here, the acceleration pulse is an acceleration drive amount required to decelerate and stop the focus lens holding frame 12 at the target position, and is stored in the ROM in advance.

“Step 125” Since it is determined in step 124 that the pulse count value at the current position is the acceleration region, the lens CPU 21 performs the acceleration process.
“Step 126” The lens CPU 21 determines whether or not the remaining drive amount P _t −P _c up to the target position is equal to or less than a predetermined deceleration pulse P _d . If it is less than the deceleration pulse, the process proceeds to step 127. If it is greater than the deceleration pulse, the process proceeds to step 128.

  Here, the deceleration pulse is a deceleration driving amount necessary for decelerating and stopping the focus lens holding frame 12 at the target position, and is stored in the ROM in advance.

“Step 127” Since it is determined in step 126 that the pulse count value at the current position is the deceleration region, the lens CPU 21 performs a deceleration process.
“Step 128” Since it is determined in step 126 that the pulse count value at the current position has not reached the deceleration region, the lens CPU 21 fixes the speed to the highest speed and performs constant speed driving.
“Step 129” The lens CPU 21 performs a speed control process. Here, the speed control process compares the current drive speed with the target drive speed, and increases or decreases the drive speed so as to approach the target drive speed.

In this embodiment, since a DC motor is used as the lens driving motor, the driving speed is increased or decreased by changing the voltage applied to the DC motor.
"Step 130"
The lens CPU 21 determines whether or not the remaining drive amount P _t −P _c up to the target position is zero. If the remaining drive amount is 0, the process proceeds to step 131 of FIG. 5, and if the remaining drive amount is not 0, the process returns to step 121.

  In this way, the lens CPU 21 accelerates the focus lens holding frame 12 so as to reach the target position quickly, and when reaching the highest speed before starting deceleration, performs constant speed driving at the highest speed, When entering the deceleration area, start deceleration. When the remaining drive amount becomes 0, the operation proceeds to the next stop operation.

Next, the processing operation when the photographing lens 2 of FIG. 5 is stopped will be described.
“Step 131” Since the remaining movement amount P _t −P _c of the focus lens holding frame 12 to the target position is 0 in Step 130, the lens CPU 21 outputs a control signal to the brake drive circuit 27 and supplies power to the brake unit 28. To start. As a result, the focus lens holding frame 12 is fixed.
“Step 132” The lens CPU 21 outputs a control signal to the lens driving circuit 22 and ends energization of the lens driving motor 23.
“Step 133” The lens CPU 21 outputs a control signal to the brake drive circuit 27 and ends energization of the brake unit 28.
“Step 134” The lens CPU 21 resets a focus driving flag, which is one piece of information transmitted on the camera 1 side through lens status communication. When this flag is reset, the camera 1 side shifts to the next sequence such as outputting a focus detection command to the photographing lens 2 side again or performing an exposure operation on the image sensor. become.
“Step 135” The driving process on the photographing lens 2 side is terminated.

  In this way, the brake control circuit 27 drives the brake unit (brake means) 28 before stopping the photographing lens 2 when the photographing lens 2 reaches the predetermined stop position according to the focus drive command from the camera 1. Let The brake is applied while the focus lens holding frame 12 is being driven (before the driving force disappears). In the state where the position of the focus lens holding frame 12 is fixed at a predetermined stop position, the lens driving motor 23 is de-energized to finish driving the photographing lens 2, and then the driving of the brake unit 28 is finished. Thereby, the focus lens holding frame 12 can be stopped at a desired position regardless of the play of the deceleration unit 24.

  6 and 7 are schematic views of a specific configuration of the photographing lens 2 used in the optical apparatus of the present embodiment. 6 is a cross-sectional view of the photographic lens 2 as viewed from above, and FIG. 7 is a developed perspective view of the photographic lens. Reference numeral 30 denotes a fixed cylinder constituting the main body of the photographic lens 2, and a bayonet mount 31 for coupling to a camera (not shown) is fastened to the rear end of the fixed cylinder 30 by a screw (not shown). A cam ring 32 is rotatably supported with respect to the fixed cylinder 30 and rotates in conjunction with a zoom ring 33 for performing a zooming operation.

  34 is a male helicoid ring, 35 is a female helicoid ring, and the helicoid portions 34a and 35a are screwed together. The focus lens holding frame 36 that holds the focus lens group L1 is fastened to the male helicoid ring 34 by screws (not shown). On the outer peripheral portion of the male helicoid ring 34, a protrusion 34b that engages with a straight groove (not shown) formed on the inner peripheral portion of the focus ring 37 is provided. By applying a force in the rotational direction to the focus ring 37, the focus lens group L1 can be moved in the optical axis direction from the screwed relationship between the helicoid portions 34a and 35a in the male helicoid ring 34 and the female helicoid ring 35. A gear portion (not shown) exists at the rear end of the inner peripheral portion of the focus ring 37 and meshes with an output gear 39 that is rotatably attached to a gear unit (gear train) 38 that is the reduction unit 24. At the time of autofocus selection, the DC motor 40 that is the lens driving motor 23 is controlled and driven in accordance with a drive command from the camera CPU 8, and a force in the rotational direction is applied to the focus ring 37 via the gear unit 38.

  A shake correction lens unit 41 is fastened to the front end of the fixed cylinder 30 with a screw (not shown). The shake correction lens unit 41 holds the shake correction lens unit L2 so as to be movable in the vertical and horizontal directions on the substantially vertical plane of the optical axis, and the shake correction lens in a direction to cancel the image shake caused by the shake of the photographing lens 2. The group L2 is driven.

  L3 is a zoom lens group. The zoom lens holding frame 42 that holds the zoom lens group L3 is provided with zoom lens rollers 46 that fit into the rectilinear groove 30a of the fixed cylinder 30 and the cam groove 32a of the cam ring 32, respectively, on the outer periphery thereof. Further, the female helicoid ring 35 is provided with a female helicoid ring roller 47 fitted on the inner periphery of the female helicoid ring 35 so as to be fitted in the straight groove 30a of the fixed cylinder 30 and the cam groove 32a of the cam ring 32, respectively. When a rotational force is applied to the zoom ring 33, the zoom lens holding frame 42 is supported by the zoom lens roller 46 so as to be movable only in the optical axis direction by the rectilinear groove 30 a of the fixed cylinder 30. It moves in the optical axis direction according to the locus of the cam groove 32a. Thus, each zoom lens unit L3 can be moved in the optical axis direction.

  Similarly, when a rotational force is applied to the zoom ring 33, the female helicoid ring 35 also moves in the optical axis direction according to the locus of the cam groove 32a of the cam ring 32. At this time, since no relative movement occurs between the female helicoid ring 35 and the focus lens holding frame 36, the focus lens group L1 is moved in the optical axis direction in the same manner as the female helicoid ring 35. 52 is a nameplate ring. A diaphragm unit 43 exists between the zoom lens groups L3. The diaphragm unit 43 is driven by the power from the diaphragm drive motor 44.

  8A and 8B are explanatory diagrams of a specific configuration of the brake unit 28. FIG. 8A is a cross-sectional view as viewed from the top of the brake unit 28 (part B in FIG. 6), and FIG. 8A is a cross-sectional view as viewed from the front of the brake unit 28 (part of the AA cross-section in FIG. 6). ).

  A coil 48 and a yoke 49 exist inside the focus ring 37, and a holding plate 50 having a spring property is fixed to the yoke 49. The holding plate 50 is fastened to the focus ring 37 with screws 51 and is inserted and held in a slit (not shown) of the nameplate ring 52 fitted to the front end of the focus ring 37. The coil 48 is held by a guide 37 a inside the focus ring 37. A band-shaped ferromagnetic material 53 is integrally formed inside the cylindrical wall portion of the male helicoid ring 34. The yoke 49 has a column portion 49 a passing through the winding internal space of the coil 48, and two upper and lower arm portions 49 b extending in a noncontact manner toward the cylindrical surface of the male helicoid ring 34. When a current flows through the coil 48 by a signal from the brake drive circuit 27, a magnetic flux is generated in the stacking thickness direction of the coil 48 in the winding internal space of the coil 48.

  The magnetic flux passes through the yoke column 49a existing in the winding internal space of the coil 48, exits from one arm 49b, enters the ferromagnetic material 55, and passes through it. Then, the magnetic flux becomes a closed magnetic flux that exits from the ferromagnetic body 55 in the vicinity of the other yoke arm portion 49b, enters the other yoke arm portion 49b, and returns to the yoke column portion 49a. Since the magnetic flux tends to shorten its path, Lorentz force is generated, the yoke 49 is moved toward the ferromagnetic body 53, and the yoke arm portion 49 b and the focus ring 37 are interposed via the holding plate 50. The fastened male helicoid ring 34 contacts. The male helicoid ring 34 that fastens the focus lens holding frame 36 is fixed and cannot move even when the lens driving motor 23 is being driven by contact of the strong magnetic flux closed by the ferromagnetic material 53 and the yoke arm portion 49b. When the energization of the coil 48 is cut off, the coil 48 and the yoke 49 are returned to the position before the energization by the action of the springy holding plate 50 fixed to the yoke 49, and the yoke arm portion 49b and the male helicoid ring. 34 becomes non-contact. The material of the holding plate 50 is preferably a metal having no magnetism such as SUS301 and SUS304.

  As described above, in this embodiment, the optical device includes an optical system including a plurality of lens groups, and includes at least one lens group L1 that moves in the optical axis direction and a lens group L1 that can move relatively in the optical axis direction. A lens holding frame (focus lens holding frame) 12 is provided. A lens driving motor (driving force generating means) 23 for moving the lens holding frame 12 and a deceleration unit for transmitting the driving force generated from the lens driving motor 23 to the lens holding frame 12 moving in the optical axis direction. 24. Further, a lens driving circuit (driving force control means) 22 for transmitting a control signal from the lens CPU 21 is provided.

  Further, a brake unit (brake means) 28 for fixing a lens holding frame (focus lens holding frame) 12 moving in the optical axis direction to any other lens group (zoom lens group 13) at an arbitrary position in the optical axis direction. And have. A brake drive circuit (brake control circuit) 27 that controls the brake unit 28 is provided. When the lens holding frame 12 is moved in the optical axis direction, before the start of energization of the lens driving motor 23 for moving the lens holding frame 12 (before the start of energization), the brake drive circuit 27 is operated by the brake unit. 28 is driven. As a result, the lens holding frame 12 is fixed.

  The brake drive circuit 27 determines whether the current movement direction is the same direction or the reverse direction with respect to the previous movement direction of the lens holding frame 12 moving in the optical axis direction, and according to each movement direction. A predetermined time until the brake unit 28 is released is selected. For example, the predetermined time is varied in the same direction or the reverse direction. The deceleration unit 24 tries to move the lens holding frame 12 in the optical axis direction. However, since the lens holding frame 12 is fixed by the brake unit 28, the deceleration unit 24 stops when it moves by the amount of play existing in the deceleration unit 24. End up. Thereafter, the brake unit 28 is released, energization of the lens driving motor 23 is started, and the lens holding frame 12 is driven. Then, when stopping the lens holding frame 12 moving in the optical axis direction, it is detected whether or not the lens holding frame 12 has reached a predetermined position in the optical axis direction. Then, before reaching the lens driving motor 23 for moving the lens holding frame 12 when it reaches, the brake driving circuit 27 first drives the brake unit 28. Accordingly, the lens holding frame 12 that has moved in the optical axis direction is fixed by the brake unit 28.

  Thereafter, energization of the lens driving motor 23 is terminated. At this time, even if the lens holding frame 12 is about to move in the optical axis direction, the lens holding frame 12 is fixed by the brake unit 28. Therefore, even if there is play in the deceleration unit 24, it can be stopped at a predetermined position without being affected by it. With these configurations, it is possible to reduce the stop position shift due to the play existing in the deceleration unit 24, reduce the drive delay at the start of the lens holding frame 12, and stop the lens holding frame 12 at a desired position with high accuracy. be able to. Further, in the conventional optical apparatus, in order to stop the lens holding frame with high accuracy, it is necessary to decelerate the lens holding frame to a speed at which the lens holding frame can be stopped when the power to the lens driving motor 23 is turned off. However, in this embodiment, it is only necessary that the brake unit 28 is decelerated to a speed at which the driving lens holding frame can be fixed. Therefore, it is easy to shorten the total driving time of the lens holding frame.

  In this embodiment, when the lens holding frame is started to be driven, the current movement direction is the same as or opposite to the previous movement direction of the lens holding frame in which the brake drive circuit 27 moves in the optical axis direction. The method of judging whether it is a direction was mentioned. However, the determination of the moving direction is not performed, and the brake unit 28 may be driven for a predetermined time period that can sufficiently remove the play in either moving direction.

  The above-described configuration of the brake unit 28 is an example, and the present invention is not limited to this, and a known brake means may be used. However, in the case of brake means with poor responsiveness, it is necessary to perform control in consideration of driving delay of the brake means. Although a DC motor has been described as the lens driving motor 23 described above, the present invention is not limited to this, and a known driving force generating means such as a stepping motor or an ultrasonic motor may be used. Further, the present embodiment can be applied to a film camera system and a digital camera system. Although a camera with an interchangeable photographic lens has been described, the present invention is not limited to this, and a camera with an integrated photographic lens may be used. In addition to a photographic optical system, an optical device such as a liquid crystal projector or a binocular equipped with an AF function The same applies to the above.

[Example 2]
Hereinafter, with reference to the flowchart of FIG. 9, the processing operation of automatic focus adjustment in the optical apparatus according to the second embodiment of the present invention will be described. In this embodiment, a part of the camera system having the same configuration as that of the first embodiment shown in FIGS. 1, 2 and 4 to 8 is used. However, the driving of the brake unit 28 at the start of driving the lens holding frame is performed. The determination process for canceling is different from that in the first embodiment.

  In this embodiment, the movement of the lens drive motor 23 or the deceleration unit 24 is detected by a drive detection means (pulse generator 29). And the time which cancels the drive of the brake unit 28 is controlled based on the detection result. For example, after confirming the stop, the drive of the brake unit 27 is released. FIG. 9 is a flowchart of processing at the time of starting the photographing lens 2 on the photographing lens 2 side (mainly the lens CPU 21). In FIG. 9, the portions with circled numbers indicate that they are connected to the circled numbers in FIG. 4.

“Step 211” The lens CPU 21 receives a focus drive command from the camera 1 side through communication at step 106 in FIG.
“Step 212” The lens CPU 21 sets a focus driving flag, which is one piece of information to be transmitted to the camera 1 in the lens status communication in step 107 of FIG. 2 described above. While this flag is set, the camera 1 determines that the focus lens holding frame 12 is being driven.
“Step 213” The lens CPU 21 stores the focus drive amount transmitted from the camera 1 side in step 111 of FIG. 3 in a memory in the lens CPU 21.
“Step 214” The lens CPU 21 includes a pulse width measurement timer for measuring the time from the rise to the fall of the pulse signal output from the pulse generator 29 and the time from the fall to the rise of the next pulse signal. Yes. That is, the time during which the output signal from the pulse generator 29 does not change is measured.
“Step 215” The lens CPU 21 outputs a control signal to the brake drive circuit 27 and starts energizing the brake unit 28. Thereby, the focus lens holding frame 12 is fixed.

“Step 216” The lens CPU 21 outputs a control signal to the lens driving circuit 22 and starts energizing the lens driving motor 23. At this time, the focus lens holding frame 12 is fixed by the brake unit 28 and does not move.
“Step 217” The lens CPU 21 determines whether or not a pulse signal is input from the pulse generator 29. If no pulse signal is input, the process proceeds to step 218. If there is an input, the process returns to step 216.
“Step 218” The lens CPU 21 reads R-TIM which is the current value of the pulse width measurement timer. This R-TIM represents the time from the previous pulse input (rising edge of the pulse signal) to the present time.
“Step 219” The lens CPU 21 compares R-TIM and STOP-TIM. Here, STOP-TIM is a state in which there is no change in the output signal from the pulse generator 29, which is stored in a predetermined memory for determining that the focus lens holding frame 12 (lens driving motor) has stopped. Is the time. If R-TIM is equal to or greater than STOP-TIM, the process proceeds to step 220. If R-TIM is smaller than STOP-TIM, the process returns to step 216.
“Step 220” The lens CPU 21 outputs a control signal to the brake drive circuit 27 and ends energization to the brake unit 28. As a result, the focus lens holding frame 12 is driven.

  In addition, since this embodiment is the same as the first embodiment except for the configuration described above, detailed description thereof is omitted. In this way, on the photographic lens 2 side, after receiving the focus drive command from the camera 1 side, the brake unit 28 is driven before the focus lens holding frame 12 is driven, and the focus lens holding frame 12 is braked and fixed. The lens drive is started during the operation. Although the deceleration unit 24 tries to drive, the focus lens holding frame 12 cannot be moved by the brake unit 28, so the play in the deceleration unit 24 is clogged.

  Here, the drive state of the speed reduction unit 24 is confirmed by the pulse signal input from the pulse generator 29 serving as the drive detection means, and when the speed reduction unit 24 is stopped, the play of the speed reduction unit 24 is finished. The brake drive circuit 27 ends the drive of the brake unit 28. As a result, the deceleration unit 24 starts driving the focus lens holding frame 12 from a state where there is no backlash.

  In the first embodiment, since the deceleration unit 24 drives the brake means within a predetermined time that can sufficiently remove the rattling, the brake means is actually driven until a predetermined time elapses even when the rattling is finished. Sometimes. However, in this embodiment, the driving time can be further shortened because the driving of the brake means can be finished immediately after confirming that the play of the speed reduction unit 24 has been finished by the drive detecting means.

  As described above, according to the optical device of the present invention, when the lens holding frame is moved in the optical axis direction, the brake control means is generated prior to the generation of the driving force of the driving force generating means for moving the lens holding frame. Drives the brake means. As a result, the lens holding frame can be fixed. The driving force transmission means tries to move the lens holding frame in the optical axis direction. However, since the lens holding frame is fixed by the brake means, the driving force transmission means stops when it moves by the amount of play existing in the driving force transmission means.

  Further, when the lens holding frame moving in the optical axis direction is stopped, the brake control means drives the brake means prior to the disappearance of the driving force of the driving force generating means for moving the lens holding frame. . Thereby, the lens holding frame can be fixed. Even if the lens holding frame is about to move in the optical axis direction, the lens holding frame is fixed by the brake means. Therefore, even if there is play in the driving force transmission means, the lens holding frame can be stopped at a desired position without being affected. For this reason, it is possible to reduce the deviation between the control signal to the driving force generating means and the actual lens driving state caused by the play in the driving force transmitting means. Thereby, the driving delay at the time of starting the lens holding frame can be reduced, and the lens holding frame can be stopped at a desired 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.

8 Camera CPU 11 Focus lens 12, 36 Focus lens holding frame 13 Zoom lens 21 Lens CPU 22 Lens drive circuit 23 Lens drive motor 24 Deceleration unit 27 Brake drive circuit 28 Brake unit

Claims (9)

  In a photographing optical system having a plurality of lens groups, at least one lens group that is relatively movable in the optical axis direction, a lens holding frame that holds the lens group that is relatively movable in the optical axis direction, and the lens holding frame Driving force generating means for moving, driving force transmitting means for transmitting the driving force generated from the driving force generating means to the lens holding frame, driving force control means for controlling the driving of the driving force generating means, An optical apparatus comprising: brake means for fixing the lens holding frame at an arbitrary position in the optical axis direction; and brake control means for controlling the brake means.   When driving the lens holding frame in the optical axis direction by the driving force control means, prior to generation of the driving force of the driving force generation means for moving the lens holding frame, the brake control means The lens holding frame is fixed by driving the brake means, and after a predetermined time has elapsed since the driving of the driving force generating means is started, the driving of the brake means is released, and the lens holding frame is 2. The optical apparatus according to claim 1, wherein driving is started.   When the lens holding frame is driven in the optical axis direction by the driving force control unit, the brake control unit is configured to perform the predetermined time from when the driving force generation unit starts to be released until the brake unit is released. 3. The optical apparatus according to claim 2, wherein the optical device is made different from the previous movement direction of the lens holding frame depending on whether the current movement direction is the same direction or the reverse direction.   In an optical system comprising a plurality of lens groups, at least one lens group that is relatively movable in the optical axis direction, a lens holding frame that holds a lens group that is relatively movable in the optical axis direction, and the lens holding frame is moved Driving force generating means for causing the driving force generating means to transmit driving force generated from the driving force generating means to the lens holding frame, driving force control means for controlling the driving force generating means, and the driving force Drive detecting means for detecting the movement of the generating means or the driving force transmitting means; brake means for fixing the lens holding frame at an arbitrary position in the optical axis direction; and brake control means for controlling the brake means. An optical device characterized by the above.   5. The optical apparatus according to claim 4, wherein the brake control unit releases the driving of the brake unit after confirming the stop of the driving force generation unit or the driving force transmission unit by the drive detection unit. .   The driving force generating means for the brake control means to move the lens holding frame when stopping and fixing the lens holding frame moving in the optical axis direction by the driving force from the driving force generating means. 5. The optical device according to claim 1, wherein the lens holding frame is fixed at a predetermined position in the optical axis direction by driving the brake unit before the driving force from the optical axis disappears. 6. apparatus.   The optical apparatus according to claim 1, wherein the driving force generation unit uses a DC motor.   The optical apparatus according to claim 1, wherein the driving force transmission unit uses a gear train.   The optical apparatus according to claim 1, wherein the lens group that is relatively movable in the optical axis direction is a focus lens group.