JP7490441B2 - Optical Instruments - Google Patents

Description

The present invention relates to an optical device that moves a built-in lens.

Optical devices such as digital cameras, video cameras, and interchangeable lenses that perform focusing and zooming by moving the built-in lens are equipped with a focus drive mechanism that consists of a reduction gear and an actuator and moves the focus group including the lens. The focus drive mechanism transmits the driving force of the actuator to the cam barrel via the reduction gear to rotate it, and guides the moving rollers of the focus group that fit into the cam grooves of the cam barrel in the direction of the optical axis.

In focusing and zooming, a reference signal indicating a reference position is generated, and the reference signal is used as a starting point to operate the actuator and move the focus group to the desired position. If it takes time to generate the reference signal, the focusing and zooming operations cannot be started quickly, which can lead to missed photographic opportunities, particularly in optical devices where the focus group has a long distance to move and therefore requires time to move.

A reference signal generating mechanism is known in which a rib that rotates together with the cam barrel passes through a slit in a gate-shaped photointerrupter, and a reference signal is generated when the end of the rib in the rotational direction passes through the slit (see, for example, Patent Document 1). In optical devices in which the focus group moves a long distance, multiple photointerrupters are provided in the movement range of the rib that corresponds to the movable range of the focus group. In this case, even a small movement of the focus group increases the likelihood that the end of the rib of the cam barrel, which rotates in conjunction with the focus group, will pass through the slit in one of the photointerrupters, allowing the reference signal to be generated in a short time.

Patent No. 5473341

However, for example, if two photointerrupters are arranged in series along the rotation direction on the outer periphery of the cam barrel, a rib must pass through the slits of each photointerrupter, and the rib extends a long way in the rotation direction. Because this rib protrudes from the outer periphery of the cam barrel, the peripheral components of the cam barrel must avoid interference with the rib over a wide area, which increases the size of the peripheral components. Also, in this case, the two photointerrupters must be arranged at a large distance from each other in correspondence with the ribs, which increases the size of the flexible board on which the two photointerrupters are mounted, and increases the cost of the optical device. In other words, it becomes difficult to achieve a miniaturized optical device, which increases the size of the optical device and leads to an increase in costs.

The object of the present invention is to provide an optical device that can generate a reference signal in a short time while suppressing increases in cost and size.

In order to achieve the above object, an optical device of the present invention includes a drive mechanism having a lens group movable in an optical axis direction, and a cam barrel that rotates around the optical axis to move the lens group by a cam mechanism, the drive mechanism having a motor that drives the cam barrel to rotate, a first rib and a second rib provided on an outer circumferential surface of the cam barrel, and a first detection element and a second detection element provided corresponding to each of the ribs, the first rib and the second rib are arranged parallel to each other so as to extend in a rotational direction of the cam barrel and rotate together with the rotation of the cam barrel, and the first detection element and the second detection element are positioned the first detection element and the second detection element each detect the passage of the starting point of the corresponding rib at a timing different from each other; the length of the second rib is shorter than the length of the first rib; the second rib is arranged to overlap the first rib when viewed along the optical axis direction; and the first detection element and the second detection element are arranged to overlap at least partially when viewed along a direction perpendicular to the optical axis direction.

The present invention makes it possible to generate a reference signal in a short time in an optical device while suppressing increases in cost and size.

1 is a perspective view showing a schematic external view of an interchangeable lens, which is an example of an optical device according to an embodiment of the present invention. FIG. 2 is a block diagram showing the electrical and optical configurations of the interchangeable lens and the camera body of FIG. 1 . 2 is a cross-sectional view for explaining the positional relationship of components in the interchangeable lens and the camera body in FIG. 1 . 2 is a cross-sectional view for explaining the positional relationship of components in the interchangeable lens and the camera body in FIG. 1 . 2 is an exploded view for explaining in detail the configuration of a focus drive mechanism in the interchangeable lens of FIG. 1 . 2 is an exploded view for explaining in detail the configuration of a focus drive mechanism in the interchangeable lens of FIG. 1 . 1A to 1C are diagrams for explaining the positional relationship between a first rib, a second rib, a first PI, and a second PI in an embodiment of the present invention. 10 is a diagram for explaining the arrangement of light-emitting units and light-receiving units of a first PI and a second PI. FIG. FIG. 13 is a diagram for explaining a method of holding a first PI and a second PI. 11 is a perspective view showing the positional relationship between the focus group, a first rib, a second rib, a first PI, and a second PI in each movement area of the focus group. FIG. 11 is a graph showing how signals generated by a first PI and a second PI change as the focus group moves.

The following describes in detail an embodiment of the present invention with reference to the drawings. In this embodiment, the present invention is described as being applied to an interchangeable lens, which is an example of an optical device. However, the present invention can also be applied to other optical devices such as digital cameras and video cameras with integrated lenses, and various modifications and variations are possible within the scope of the invention.

Figure 1 is a perspective view showing a schematic appearance of an interchangeable lens, which is an example of an optical device according to this embodiment. In Figure 1, an interchangeable lens 101 is shown attached to a camera body 1, and the optical axis direction of the imaging optical system housed in the interchangeable lens 101 is defined as the X-axis direction, and two directions perpendicular to the X-axis direction are defined as the Z-axis direction and the Y-axis direction. The Z-axis direction and the Y-axis direction are perpendicular to each other, and when the camera body 1 is held horizontally, the Z-axis direction coincides with the approximately horizontal direction, and the Y-axis direction coincides with the approximately vertical direction. In addition, the rotation direction around the Z-axis is defined as the Pitch direction, and the rotation direction around the Y-axis is defined as the Yaw direction.

As shown in FIG. 1(A), a grip section 2 for a user to hold the camera body 1 with their hand is provided on the left side when viewed from the front (subject side) of the camera body 1 (the right side when viewed from the back of the camera body 1). A power operation section 3 is also located on the top surface of the camera body 1. When the user turns on the power operation section 3 while the camera body 1 is in the power-off state, the camera body 1 is turned on and image capture becomes possible. When the user turns off the power operation section 3 while the camera body 1 is in the power-on state, the camera body 1 is turned off.

On the top surface of the camera body 1, a mode dial 4, a release button 5, and an accessory shoe 6 are provided. The user can switch between imaging modes by rotating the mode dial 4. The imaging modes include a manual still image imaging mode in which the user can set imaging conditions such as shutter speed and aperture value as desired, an auto still image imaging mode in which an appropriate exposure amount is automatically obtained, and a video imaging mode for capturing videos. In addition, the user can instruct imaging preparation operations such as autofocus and auto exposure control by half-pressing the release button 5, and can instruct imaging by fully pressing the button. An accessory such as an external flash is detachably attached to the accessory shoe 6. In addition, an imaging element that photoelectrically converts (captures) the subject image formed by the imaging optical system in the interchangeable lens 101 is provided inside the camera body 1.

The interchangeable lens 101 is mechanically and electrically connected to a camera mount 7 provided on the camera body 1 via a lens mount 102. Inside the interchangeable lens 101 is housed an imaging optical system that focuses light from a subject to form a subject image.

As shown in FIG. 1B, a rear operation unit 8 and a display unit 9 are provided on the rear of the camera body 1. The rear operation unit 8 includes a number of buttons and dials to which various functions are assigned. When the camera body 1 is powered on and the still image capture mode or video capture mode is set, a through image of a subject captured by the image sensor is displayed on the display unit 9. The display unit 9 also displays imaging parameters indicating imaging conditions such as shutter speed and aperture value, and the user can change the settings of the imaging parameters by operating the rear operation unit 8 while viewing the display. The rear operation unit 8 includes a playback button for instructing playback of a recorded captured image, and the captured image is played back and displayed on the display unit 9 when the user operates the playback button.

2 is a block diagram showing the electrical and optical configurations of the interchangeable lens 101 and the camera body 1. In FIG. 2, the camera body 1 has a power supply unit 10 that supplies power to the camera body 1 and the interchangeable lens 101, and an operation unit 11 including a power operation unit 3, a mode dial 4, a release button 5, a rear operation unit 8, and a touch panel mechanism of the display unit 9. The camera control unit 12 provided in the camera body 1 and the lens control unit 104 provided in the interchangeable lens 101 are linked to each other to control the camera body 1 and the interchangeable lens 101 as a whole. The camera control unit 12 reads and executes a computer program stored in the memory unit 13. At that time, the camera control unit 12 communicates with the lens control unit 104 with various control signals, data, etc., via a communication terminal of an electrical contact 105 provided in the lens mount 102. The electrical contact 105 includes a power terminal that supplies power supplied from the power supply unit 10 to the interchangeable lens 101.

The imaging optical system of the interchangeable lens 101 has a focus group 201 (lens group) including a focus lens that moves in the optical axis direction to adjust the focus, an aperture group 401 that adjusts the amount of light, and an anti-vibration group 510 including a shift lens as an anti-vibration element that reduces image blur. The anti-vibration group 510 performs an anti-vibration operation to reduce image blur by moving (shifting) the shift lens in a plane parallel to the Z-axis direction and the Y-axis direction perpendicular to the optical axis. Furthermore, the interchangeable lens 101 has a focus driver 301 that drives the focus group 201, an aperture driver 402 that drives the aperture group 401, and an anti-vibration driver 520 that drives the anti-vibration group 510.

The camera body 1 has a shutter unit 14, a shutter drive unit 15, an image sensor 16, an image processing unit 17, a focus detection unit 18, a display unit 9, and a camera control unit 12. The shutter unit 14 adjusts the amount of light collected by the imaging optical system in the interchangeable lens 101 and exposed by the image sensor 16. The image sensor 16 photoelectrically converts the subject image formed by the imaging optical system and outputs an image signal. The image processing unit 17 performs various image processes on the image signal to generate an image signal. The display unit 9 displays the image signal (through image) output from the image processing unit 17, displays imaging parameters, or plays back and displays an image recorded in the memory unit 13 or a recording medium (not shown).

The camera control unit 12 controls the driving of the focus group 201 in response to an image capture preparation operation (half-pressing the release button 5) in the operation unit 11. For example, when autofocus is instructed, the focus detection unit 18 determines the focus state of the subject image formed by the image sensor 16 based on the image signal generated by the image processing unit 17, generates a focus signal, and transmits it to the camera control unit 12. At the same time, the focus drive unit 301 detects the current position of the focus group 201 and transmits a signal indicating the current position to the camera control unit 12 via the lens control unit 104. The camera control unit 12 compares the focus state of the subject image with the current position of the focus group 201, calculates the focus drive amount from the amount of deviation, and transmits it to the lens control unit 104. The lens control unit 104 then controls the drive of the focus group 201 to the target position via the focus drive unit 301, and corrects the focus deviation of the subject image.

The focus drive unit 301 includes a cam barrel, a drive motor, a reduction gear that connects the cam barrel and the drive motor, and a photointerrupter (hereinafter abbreviated as "PI") that detects the reference position of the focus group 201. The detailed configuration of the focus drive unit 301 will be described later. A DC motor with an encoder or an ultrasonic motor may be used as the drive motor. The PI directly receives light emitted from the light emitting unit at the light receiving unit, but instead of the PI, a photoreflector that receives reflected light from a reflecting surface or a brush that contacts the conductive pattern may be used.

The camera control unit 12 controls the driving of the aperture group 401 and the shutter unit 14 via the aperture drive unit 402 and the shutter drive unit 15 in response to the aperture value and shutter speed settings set by the operation unit 11. For example, when automatic exposure control is instructed, the camera control unit 12 receives a luminance signal generated by the image processing unit 17 and performs a photometric calculation. Then, based on the result of this photometric calculation, the camera control unit 12 controls the driving of the aperture group 401 in response to the user's image capture instruction operation (full press of the release button 5) on the operation unit 11. The camera control unit 12 also controls the driving of the shutter unit 14 via the shutter drive unit 15 and performs exposure processing by the image sensor 16.

The camera body 1 has a pitch shake detection unit 19 and a yaw shake detection unit 20 that detect image shake such as hand shake caused by the user. The pitch shake detection unit 19 and the yaw shake detection unit 20 use an angular velocity sensor (vibration gyro) and an angular acceleration sensor to detect image shake in the pitch direction and the yaw direction, respectively, and output a shake signal. The camera control unit 12 calculates the shift position of the vibration isolation group 510 (shift lens) in the Y-axis direction using the shake signal from the pitch shake detection unit 19. Similarly, the camera control unit 12 calculates the shift position of the vibration isolation group 510 in the Z-axis direction using the shake signal from the yaw shake detection unit 20. Then, the camera control unit 12 controls the drive of the vibration isolation group 510 to a target position according to the calculated shift position in the pitch direction and the shift position in the yaw direction, and performs an anti-shake operation to reduce image shake during exposure and during display of a through image.

Figures 3 and 4 are cross-sectional views for explaining the positional relationship of components in the interchangeable lens 101 and the camera body 1. The cross-sectional views of Figures 3 and 4 show cross-sectional views of the interchangeable lens 101 and the camera body 1 cut along planes parallel to the X-axis and Y-axis directions, and respectively show the retracted and extended states of the focus group 201. The center line shown in Figures 3 and 4 (dash line in the figures) approximately coincides with the optical axis of the imaging optical system. In other words, the center line is synonymous with the optical axis.

In this embodiment, as an example of an imaging optical system, a two-group configuration consisting of a focus group 201 including a first focus lens 211 and a second focus lens 212, and a fixed group 601 including a first fixed lens 611 and a second fixed lens 612 will be described.

The focus group 201, which has moved to a predetermined optical position in response to the defocus of the subject image, forms an image of the light from the subject on the imaging surface of the image sensor 16 via the fixed group 601. At this time, the aperture group 401 is housed in the focus group 201 together with the first focus lens 211 and the second focus lens 212, and moves integrally with the focus group 201. On the other hand, the vibration isolation group 510 is disposed between the first fixed lens 611 and the second fixed lens 612, and functions as part of the fixed group 601.

Furthermore, the imaging optical system of this embodiment has an adjustment mechanism that intentionally shifts the position of the second focus lens 212 in order to maintain the optical performance of the imaging optical system as a whole. This allows workers in the assembly process to eliminate adverse effects on optical performance, such as manufacturing errors and assembly variations that occur in each component, while checking the overall optical performance state.

Figures 5 and 6 are exploded views for explaining in detail the configuration of the focus drive mechanism in the interchangeable lens 101. The focus drive mechanism is made up of a focus group 201 and a focus drive unit 301. Figure 5(A) shows the focus group 201 and focus drive unit 301 in an assembled state, Figure 5(B) shows the focus drive mechanism disassembled into the focus group 201 and focus drive unit 301, and Figure 6 shows the focus drive unit 301 in an disassembled state.

The fixed barrel 106, which is a fixed member of the focus drive unit 301, holds the first fixed lens 611 on its inner circumference side, and holds the linear guide barrel 107, which is a fixed member, on the subject side. The linear guide barrel 107 houses the focus group 201 on its inner circumference side, and holds a cam barrel 108 that can rotate around the optical axis on its outer circumference side. The cam barrel 108 is biased toward the imaging surface in the optical axis direction by an elastic member 109, and the imaging surface side of the image sensor (camera body 1 side) is in close contact with the fixed barrel 106 so as to be slidable against it. This reduces rattling of the cam barrel 108 in the optical axis direction.

The drive motor 310 of the focus drive unit 301 is fixed to the end face of the fixed tube 106 on the subject side so that its rotation axis is parallel to the optical axis. A first reduction gear 321 is fixed to the rotation axis of the drive motor 310. The second reduction gear 322, the third reduction gear 323, and the fourth reduction gear 324 of the focus drive unit 301 are each rotatably held on the end face of the fixed tube 106 on the imaging surface side. Specifically, the rotation axes of the second reduction gear 322, the third reduction gear 323, and the fourth reduction gear 324 on the subject side are held in holding holes provided on the end face of the fixed tube 106 on the imaging surface side. The rear side axes of the second reduction gear 322, the third reduction gear 323, and the fourth reduction gear 324 are held by holding holes provided in the gear cover 341. The gear cover 341 is fixed to the fixed barrel 106 so as to sandwich the second reduction gear 322, the third reduction gear 323, and the fourth reduction gear 324.

The cam barrel gear 330 of the focus drive unit 301 is fixed to the outer circumferential surface of the cam barrel 108 so as to engage with the fourth reduction gear 324. When the drive motor 310 rotates, the driving force is reduced through the first reduction gear 321, the second reduction gear 322, the third reduction gear 323, the fourth reduction gear 324, and the cam barrel gear 330, and then transmitted to the cam barrel 108. As a result, the cam barrel 108 rotates about the optical axis while its movement in the optical axis direction is restricted by the elastic member 109.

The focus group 201 is an assembly member including a substantially cylindrical focus lens, and has a plurality of moving rollers 231 (cam mechanism) arranged at equal intervals of 120° in the circumferential direction on the outer circumferential surface. The moving rollers 231 are engagement members that protrude in the radial direction of the focus group 201, and engage with the linear grooves 111 of the linear guide tube 107 described later. The focus group 201 is inserted into the inner circumferential side of the linear guide tube 107 from the subject side of the linear guide tube 107 and assembled. The linear guide tube 107 has three through grooves 111 formed on its inner circumferential surface that extend in the optical axis direction. All of these through grooves have the same groove width. By engaging each moving roller 231 of the focus group 201 with the linear grooves 111, the linear guide tube 107 restricts the movement of the focus group 201 in the rotational direction and guides the linear movement of the focus group 201 in the optical axis direction.

A cam groove 112 (cam mechanism) having a linear trajectory that is inclined in the direction of rotation is formed on the inner peripheral surface of the cam barrel 108 of the focus drive unit 301 in response to the stroke (amount of movement in the optical axis direction) of the focus group 201. The cam groove 112 is composed of three non-penetrating, bottomed grooves that are arranged to correspond to each moving roller 231. Each cam groove 112 describes the same cam trajectory and has the same groove width and depth.

When the focus group 201 is assembled into the linear guide barrel 107, each moving roller 231 engages with the corresponding linear groove 111, and the top of each moving roller 231 protruding from the linear groove 111 engages with the corresponding cam groove 112. Each moving roller 231 engages with the corresponding linear groove 111 and cam groove 112, forming a small gap between them. When the cam barrel 108 rotates, the moving rollers 231 that engage with the corresponding linear groove 111 and cam groove 112 move along the cam locus of the cam groove 112, thereby moving the focus group 201 forward and backward in the optical axis direction.

The fixed barrel 106 holds a gate-shaped first PI 371 (detection element) and a second PI 372 (detection element). In the first PI 371 and the second PI 372, the light-emitting section and the light-receiving section are arranged facing each other to form a slit. If a rib or the like is sandwiched in the slit, the light from the light-emitting section is blocked and not received by the light-receiving section, generating a low signal. If nothing is sandwiched in the slit, the light from the light-emitting section is received by the light-receiving section, generating a high signal.

A first rib 331 (detected portion) and a second rib 332 (detected portion) for detecting a reference position are formed on the outer periphery of the cam barrel gear 330 and extend in the rotational direction of the cam barrel 108. When the cam barrel 108 is in close contact with the fixed barrel 106, the first rib 331 is sandwiched in the slit of the first PI 371, and the second rib 332 is sandwiched in the slit of the second PI 372.

While the first rib 331 is sandwiched in the slit of the first PI 371, the first rib 331 blocks the light from the light-emitting unit, so the first PI 371 generates a Low signal. When the cam barrel 108 rotates and the end of the first rib 331 passes through the slit of the first PI 371, the light from the light-emitting unit is no longer blocked, or the light from the light-emitting unit is blocked. At this time, the signal generated by the first PI 371 changes from Low to High, or from High to Low. The timing at which this signal switches is used as a reference signal.

Also, while the second rib 332 is sandwiched in the slit of the second PI 372, the second rib 332 blocks the light from the light-emitting unit, so the second PI 372 generates a Low signal. When the cam barrel 108 rotates and the end of the second rib 332 passes through the slit of the second PI 372, the light from the light-emitting unit is no longer blocked, or the light from the light-emitting unit is blocked. At this time, too, the signal generated by the second PI 372 changes from Low to High, or from High to Low. Again, the timing at which this signal switches is used as a reference signal.

Generally, a stepping motor, which is a type of actuator, is used as the drive motor in the focus drive unit. However, a stepping motor can only control the relative drive amount and does not perform drive control based on a reference position, so the current position of the focus group 201 is not determined in the power-off state. Therefore, when the user turns on the power operation unit 3, it is necessary to move the focus group 201 to the reference position once. In order to know the reference position early, it is preferable to set multiple reference positions in the stroke of the focus group 201.

In response to this, the focus drive mechanism according to this embodiment is configured so that the timing at which the signal generated by the first PI 371 switches is different from the timing at which the signal generated by the second PI 372 switches. Specifically, these components are arranged so that the timing at which the first rib 331 passes through the slit of the first PI 371 is different from the timing at which the second rib 332 passes through the slit of the second PI 372. The first rib 331 has a first starting point 331a and a third starting point 331b as ends in the rotation direction. The second rib 332 has a second starting point 332a as an end in the rotation direction. That is, in this embodiment, three reference positions are set.

However, since the first rib 331 and the second rib 332 protrude from the outer periphery of the cam barrel 108, the peripheral components of the cam barrel 108 need to avoid interference with the first rib 331 and the second rib 332. In this case, if the first rib 331 and the second rib 332 are arranged so as to occupy a large area on the outer periphery side of the cam barrel 108, the degree of freedom in arranging the peripheral components is reduced in order to avoid these ribs, and it becomes difficult to arrange each peripheral component spatially efficiently. In addition, since the first rib 331 and the second rib 332 are formed on the cam barrel gear 330, the cam barrel gear 330 becomes large. As a result, the cost of the focus drive mechanism and, by extension, the interchangeable lens 101 increase and become larger. In this embodiment, the arrangement of the first rib 331, the second rib 332, the first PI 371, and the second PI 372 is devised to deal with this.

7A, if the first rib 331 and the second rib 332 are arranged so as not to overlap when viewed along the optical axis direction indicated by the solid arrow in the figure, the first rib 331 and the second rib 332 extend long in the rotational direction of the cam barrel 108. In this case, the extension length of the first rib 331 and the second rib 332 as shown in the figure is defined as _L0 .

7B, when the first PI 371 and the second PI 372 are arranged so as not to overlap when viewed along a direction perpendicular to the optical axis direction indicated by the dashed arrow in the figure, the first PI 371 and the second PI 372 extend long in the optical axis direction. In this case, the extension length of the first PI 371 and the second PI 372 is set to l ₀ as shown in the figure.

In contrast, in this embodiment, as shown in FIG. 7C, the first rib 331 and the second rib 332 are arranged so as to overlap at least partially when viewed along the optical axis direction. At this time, the length _L1 of the first rib 331 and the second rib 332 extending in the rotation direction of the cam barrel 108 is shorter than the length _L0 . Also, the first PI 371 and the second PI ₃₇₂ are arranged so as to overlap at least partially when viewed along a direction perpendicular to the optical axis direction. At this time, the length l1 of the first PI 371 and the second PI 372 extending in the optical axis direction is shorter than the length _l0 . The first rib 331 and the second rib 332 are arranged along the rotation direction of the cam barrel 108 and parallel to each other.

This prevents the first rib 331 and the second rib 332 from occupying a large area on the outer periphery of the cam barrel 108, allowing for greater freedom in arranging peripheral components. It also eliminates the need to enlarge the cam barrel gear 330. Furthermore, since the area in which the first PI 371 and the second PI 372 are arranged can be reduced in association with the arrangement of the first rib 331 and the second rib 332, the flexible board (not shown) on which the two PIs are mounted can also be made smaller. As a result, it is possible to prevent the interchangeable lens 101 from increasing in cost and size.

Figure 8 is a diagram for explaining the arrangement of the light emitting section and light receiving section of the first PI 371 and the second PI 372. As described above, in this embodiment, the first PI 371 and the second PI 372 are arranged so as to overlap when viewed along a direction perpendicular to the optical axis direction indicated by the dashed arrow in the figure (Figure 8 (A)). In this case, for example, the light emitting section of the first PI 371 and the light receiving section of the second PI 372 are close to each other in the optical axis direction, so there is a risk that light emitted from the light emitting section of the first PI 371 will leak through the slit and be erroneously received by the light receiving section of the second PI 372.

In response to this, in this embodiment, the first PI 371 and the second PI 372 are arranged so that the light emitting units emit light in opposite directions to each other. For example, as shown in FIG. 8B and FIG. 8C, the light emitting unit 371a of the first PI 371 and the light emitting unit 372a of the second PI 372 may be arranged so that they overlap when viewed along a direction perpendicular to the optical axis direction. At this time, the light emitting unit 371a emits light 371c in the opposite direction to the light receiving unit 372b of the second PI 372, so that the light receiving unit 372b does not mistakenly receive the light 371c. Also, the light emitting unit 372a emits light 372c in the opposite direction to the light receiving unit 371b of the first PI 371, so that the light receiving unit 371b does not mistakenly receive the light 372c. The same effect can be obtained by arranging the light receiving portion 371b of the first PI 371 and the light receiving portion 372b of the second PI 372 so that they overlap when viewed in a direction perpendicular to the optical axis direction. As a result, erroneous detection by the first PI 371 and the second PI 372 can be prevented.

9 is a diagram for explaining a method of holding the first PI 371 and the second PI 372. In FIG. 9, the first PI 371 and the second PI 372 are both attached to the fixed barrel 106 on the outside of the cam barrel 108, and are arranged so that the slits face the cam barrel 108. Specifically, the first PI 371 and the second PI 372 are attached so as to be fitted into the mounting holes opening in the fixed barrel 106. Each mounting hole is expanded in the +X direction (toward the subject in the optical axis direction) indicated by the arrow in the figure, and the first urging portion 106a (urging means) and the second urging portion 106b (urging means) having elasticity are arranged in the expanded portion. The first urging portion 106a urges the first PI 371 in the mounting hole in the -X direction (toward the image plane in the optical axis direction) opposite to the +X direction indicated by the arrow in the figure. The second biasing portion 106b biases the second PI 372 in the -X direction indicated by the arrow in the figure in the mounting hole. As a result, the first PI 371 and the second PI 372 abut against a contact wall (not shown) provided on the imaging surface side of the fixed barrel 106, and the position in the optical axis direction is determined.

When an impact is applied to the camera body 1 or the interchangeable lens 101, the cam barrel 108 and the cam barrel gear 330 attached to the cam barrel 108 may move in the +X direction. At this time, the first rib 331 and the second rib 332 formed on the cam barrel gear 330 may also move in the +X direction and collide with the first PI 371 and the second PI 372, respectively.

In contrast, the first PI 371 and the second PI 372 are biased in the -X direction, so they have room to move in the +X direction. That is, even if the first rib 331 and the second rib 332 collide with the first PI 371 and the second PI 372, respectively, they can move in the +X direction together with the first rib 331 and the second rib 332. This makes it possible to prevent the first rib 331, the second rib 332, the first PI 371, and the second PI 372 from being damaged by the collision. In addition, at this time, the first biasing portion 106a and the second biasing portion 106b function as a cushioning material, absorbing the impact when the first rib 331 and the second rib 332 collide with the first PI 371 and the second PI 372.

Next, the process of generating a reference signal in the focus drive mechanism in this embodiment will be described. In this embodiment, the total movement area A in the optical axis direction of the focus group 201 is divided into four movement areas. Specifically, the total movement area A is divided from the imaging surface side toward the subject side into a first area A1, a second area A2, a third area A3, and a fourth area A4. In addition, the boundary between the adjacent first area A1 and second area A2 is set as a first reference position, and the boundary between the adjacent second area A2 and third area A3 is set as a second reference position. Furthermore, the boundary between the adjacent third area A3 and fourth area A4 is set as a third reference position.

Figure 10 is a perspective view showing the positional relationship of the focus group 201, the first rib 331, the second rib 332, the first PI 371, and the second PI 372 in each region. Figure 11 is a graph showing how the signals generated by the first PI 371 and the second PI 372 change as the focus group 201 moves.

In this embodiment, the positional relationship between the first rib 331 and the first PI 371 is set so that the first starting point 331a of the first rib 331 passes through the slit of the first PI 371 at the first reference position. Furthermore, the positional relationship between the second rib 332 and the second PI 372 is set so that the second starting point 332a of the second rib 332 passes through the slit of the second PI 372 at the second reference position. Furthermore, the positional relationship between the first rib 331 and the first PI 371 is set so that the third starting point 331b of the first rib 331 passes through the slit of the first PI 371 at the third reference position. As a result, the position of the focus group 201 can be grasped by the reference signals generated by the first PI 371 and the second PI 372.

Figure 10 (A) is a diagram showing a state in which the focus group 201 is located in the first area A1. The first area A1 is the area in which the focal position of the focus group 201 is located closest to infinity, the extension amount of the focus group 201 is the smallest, and the overall length of the interchangeable lens 101 is the shortest.

Normally, when the power control unit 3 of the camera body 1 is turned off, the focus group 201 moves to the first area A1 where the overall length of the interchangeable lens 101 is the shortest, i.e., where the extension amount is the smallest. After that, power supply to the interchangeable lens 101 is cut off. In other words, when the power is turned on after a normal power off operation, the first reference position is used as the reference position required to move to the desired position.

As shown in FIG. 10A, in the first region A1, the first starting point 331a, which is the end of the first rib 331 in the rotation direction (hereinafter referred to as the "positive rotation direction") when the focus group 201 is extended, does not reach the first PI 371. Therefore, the first PI 371 does not sandwich the first rib 331, and the light emitted from the light emitting portion 371a in the first PI 371 is not blocked by the first rib 331, so a High signal is generated. On the other hand, in the first region A1, the second rib 332 is sandwiched in the slit of the second PI 372, so the light emitted from the light emitting portion 372a in the second PI 372 is blocked by the second rib 332, and a Low signal is generated.

Therefore, when the lens control unit 104 recognizes that a high signal is generated from the first PI 371 and a low signal is generated from the second PI 372 when the power is turned on, it determines that the focus group 201 is in the first area A1.

Then, the lens control unit 104 controls the focus drive unit 301 so that the cam barrel 108 rotates clockwise (positive rotation direction) when viewed from the imaging surface side. As a result, the first starting point 331a passes through the slit of the first PI 371, and the signal generated by the first PI 371 changes from Hi to Low. Here, the position of the focus group 201 when the signal generated by the second PI 372 remains Low and the signal generated by the first PI 371 changes from Hi to Low is stored in advance as the first reference position in the lens control unit 104. Therefore, the lens control unit 104 can detect the first reference position by the change in the signal generated by the first PI 371. This allows the position of the focus group 201 to be specified. Then, the focus drive unit 301 is driven based on the first reference position, so that the focus group 201 can be moved to a desired position.

However, if the interchangeable lens 101 is removed from the camera body 1 with the power on, or the power supply unit 10 is removed, and power supply to the interchangeable lens 101 is cut off by a method other than turning off the power supply operation unit 3, the focus group 201 stops at the position where power supply was cut off and does not move. In such a case, when power is supplied to the interchangeable lens 101 again, the focus group 201 may be located in an area other than the first area A1, and therefore the first reference position may not be detected. In response to this, in this embodiment, in addition to the first reference position, the second reference position and third reference position described above are set. Below, a method for detecting the second reference position and the third reference position will be described.

Figure 10 (B) is a diagram showing a state in which the focus group 201 is located in the second area A2. The second area A2 is an area in which the focal position of the focus group 201 is located closer to the subject side than the first area A1, and the focus group 201 extends slightly.

As shown in FIG. 10(B), in the second region A2, the first rib 331 is sandwiched between the slits of the first PI 371, so that the light emitted from the light-emitting portion 371a in the first PI 371 is blocked by the first rib 331, generating a low signal. Also, in the second region A2, as in the first region A1, the second rib 332 is sandwiched between the slits of the second PI 372, so that the light emitted from the light-emitting portion 372a in the second PI 372 is blocked by the second rib 332, generating a low signal.

Therefore, when the lens control unit 104 recognizes that a low signal is generated from the first PI 371 and a low signal is generated from the second PI 372 when the power is turned on, it determines that the focus group 201 is in the second area A2. Then, the lens control unit 104 controls the focus drive unit 301 so that the cam barrel 108 rotates in the forward rotation direction. As a result, the second starting point portion 332a passes through the slit of the second PI 372, and the signal generated by the second PI 372 changes from low to high. Here, the position of the focus group 201 when the signal generated by the first PI 371 remains low and the signal generated by the second PI 372 changes from low to high is stored in advance as the second reference position in the lens control unit 104. Therefore, the lens control unit 104 can detect the second reference position by the change in the signal generated by the second PI 372. This allows the position of the focus group 201 to be identified.

After determining that the focus group 201 is in the second area A2, the lens control unit 104 may control the focus drive unit 301 so that the cam barrel 108 rotates in the direction opposite to the forward rotation direction. In this case, the lens control unit 104 can detect the first reference position based on a change in the signal generated by the first PI 371.

Figure 10 (C) is a diagram showing a state in which the focus group 201 is located in the third area A3. The third area A3 is an area in which the focal position of the focus group 201 is located closer to the subject side than the second area A2, and the focus group 201 extends out a large distance.

As shown in FIG. 10(C), in the third region A3, the first rib 331 is sandwiched between the slits of the first PI 371, so the light emitted from the light-emitting portion 371a in the first PI 371 is blocked by the first rib 331, generating a Low signal. On the other hand, in the third region A3, the second starting portion 332a of the second rib 332 passes through the slits of the second PI 372, so the light emitted from the light-emitting portion 372a is not blocked by the second rib 332, generating a Hi signal.

Therefore, when the lens control unit 104 recognizes that a Low signal is generated from the first PI 371 and a Hi signal is generated from the second PI 372 when the power is turned on, it determines that the focus group 201 is in the third area A3. Then, the lens control unit 104 controls the focus drive unit 301 so that the cam barrel 108 rotates in the forward rotation direction. As a result, the third starting point 331b of the first rib 331 passes through the slit of the first PI 371, and the first rib 331 is no longer sandwiched by the slit of the first PI 371, so that the signal generated by the first PI 371 changes from Low to Hi. Here, the position of the focus group 201 when the signal generated by the second PI 372 remains Hi and the signal generated by the second PI 372 changes from Low to Hi is stored in advance as the third reference position in the lens control unit 104. Therefore, the lens control unit 104 can detect the third reference position based on the change in the signal generated by the first PI 371. This allows the position of the focus group 201 to be identified.

After determining that the focus group 201 is in the third area A3, the lens control unit 104 may control the focus drive unit 301 so that the cam barrel 108 rotates in the direction opposite to the forward rotation direction. In this case, the lens control unit 104 can detect the second reference position based on a change in the signal generated by the second PI 372.

Figure 10 (D) is a diagram showing a state in which the focus group 201 is located in the fourth area A4. In the fourth area A4, the focal position of the focus group 201 is located closer to the subject side than in the third area A3, and the extension amount of the focus group 201 is the largest.

As shown in FIG. 10(D), in the fourth region A4, the third starting point 331b of the first rib 331 has passed through the slit of the first PI 371, so the light emitted from the light-emitting portion 371a is not blocked by the first PI 371, and a Hi signal is generated. Also, the second starting point 332a of the second rib 332 has passed through the slit of the second PI 372, so the light emitted from the light-emitting portion 372a is not blocked by the second rib 332, and a Hi signal is generated.

Therefore, when the power of the camera body 1 is turned on, the lens control unit 104 determines that the focus group 201 is in the fourth area A4 when it recognizes that a Hi signal is generated from the first PI 371 and a Hi signal is generated from the second PI 372. The lens control unit 104 then controls the focus drive unit 301 so that the cam barrel 108 rotates in the counterclockwise direction (opposite the forward rotation direction) when viewed from the imaging surface side. As a result, the third starting point 331b of the first rib 331 passes through the slit of the first PI 371, and the first rib 331 is sandwiched between the slits of the first PI 371, so that the signal generated by the first PI 371 changes from Hi to Low. Here, the position of the focus group 201 when the signal generated by the second PI 372 changes from Hi to Low while the signal generated by the second PI 372 remains Hi is stored in advance as a third reference position in the lens control unit 104. Therefore, the lens control unit 104 can detect the third reference position based on the change in the signal generated by the first PI 371. This allows the position of the focus group 201 to be identified.

In this embodiment, in addition to the first reference position, a second reference position and a third reference position are also set, so that when the power of the camera body 1 is turned on, the reference position required to move to the desired position can be quickly determined.

As described above, when the power operation unit 3 of the camera body 1 is turned off in the normal manner, the focus group 201 moves to the first area A1, so when the power is turned on, the focus group 201 is likely to be in the first area A1. Therefore, if the first reference position, which is the boundary between the first area A1 and the second area A2, can be quickly detected, the opportunities to quickly identify the position of the focus group 201 can be increased, which is beneficial to the user.

In this embodiment, as shown in FIG. 11, the first area A1 is set to be the narrowest compared to the second area A2, the third area A3, and the fourth area A4. This makes it possible to detect the first reference position by simply rotating the cam barrel 108 slightly in the forward direction after the power is turned on, and to quickly identify the position of the focus group 201, thereby preventing missed shooting opportunities.

There are no particular restrictions on the division of the second area A2, the third area A3, and the fourth area A4. However, by dividing the second area A2, the third area A3, and the fourth area A4 evenly, the time until the second reference position and the third reference position are detected can be made approximately equal regardless of the area in which the focus group 201 is located. This makes it possible to prevent the time it takes to detect the reference position in a certain area from being too long, improving usability for the user.

When using two PIs as in the present embodiment described above, it is also possible to provide only one common rib. In this case, the rib can be provided with projections and recesses, and the step can be used as the starting point. However, if the amount of movement of the focus group 201 is large, it is necessary to place the two PIs far apart in order to set the second area A2 to the fourth area A4. In this case, the flexible board on which the two PIs are mounted becomes large, but this embodiment is advantageous over the case of providing only one rib in that the flexible board can be prevented from becoming large by devising the arrangement of the two PIs and two ribs as described above.

The above describes a preferred embodiment of the present invention, but the present invention is not limited to the above-described embodiment, and various modifications and variations are possible within the scope of the gist of the invention.

For example, in this embodiment, the present invention is described as being applied to a focus drive mechanism that moves the focus group 201, but the present invention can be applied to any drive mechanism that can move optical components in the optical axis direction. For example, the present invention can also be applied to a zoom mechanism that changes the focal length. In addition, the cam barrel 108 and the cam barrel gear 330 may be integrated.

101 Interchangeable lens 104 Lens control unit 108 Cam barrel 201 Focus group 301 Focus drive unit 330 Cam barrel gear 331 First rib 332 Second rib 331a First starting point portion 331b Third starting point portion 332a Second starting point portion 371 First PI
371a Light emitting unit 371b Light receiving unit 372 Second PI
372a Light emitting unit 372b Light receiving unit

Claims (3)

a driving mechanism having a lens group movable in an optical axis direction and a cam barrel that rotates around the optical axis and moves the lens group by a cam mechanism;
the drive mechanism includes a motor that rotates the cam barrel, a first rib and a second rib that are provided on an outer circumferential surface of the cam barrel, and a first detection element and a second detection element that are provided corresponding to each of the ribs,
the first rib and the second rib are arranged in parallel to each other so as to extend in a rotational direction of the cam barrel and rotate together with the rotation of the cam barrel;
the first detection element and the second detection element are fixed in position, and each of the first detection element and the second detection element detects the passage of a corresponding starting point of the rib through the detection element;
the first detection element and the second detection element detect passage of the corresponding rib start point portions at different timings,
a length of the second rib is shorter than a length of the first rib, and the second rib is disposed so as to overlap with the first rib when viewed along the optical axis direction;
An optical instrument, characterized in that the first detection element and the second detection element are arranged so as to at least partially overlap when viewed along a direction perpendicular to the optical axis direction. 2. The optical device according to claim 1, further comprising a biasing means for biasing the first detection element and the second detection element in a direction opposite to a direction in which the cam barrel moves due to an external impact. each of the first detection element and the second detection element has a light emitting portion and a light receiving portion;
3. The optical device according to claim 1 , wherein the first detection element and the second detection element are arranged so as to emit light from the light-emitting portions in opposite directions to each other.