JP7435629B2 - Position detection mechanism, lens barrel and optical equipment - Google Patents

Description

The present invention relates to a position detection mechanism, a lens barrel, and an optical device.

For example, in a position detection mechanism mounted on a lens barrel or the like, it is required to detect the position with high accuracy (for example, Patent Document 1).

Japanese Patent Application Publication No. 10-170211

According to the first aspect, the position detection mechanism includes a first cylinder, a second cylinder disposed on an inner peripheral side or an outer peripheral side of the first cylinder, and a position between the first cylinder and the second cylinder. a first detection unit disposed in the third cylinder; a third cylinder; a fourth cylinder disposed on the inner circumferential side or the outer circumferential side of the third cylinder; and a fourth cylinder disposed between the third cylinder and the fourth cylinder. and a second detection section.

According to the second aspect, the lens barrel includes the position detection mechanism described above.

According to a third aspect, an optical device includes the lens barrel described above.

Note that the configurations of the embodiments described below may be modified as appropriate, and at least a portion thereof may be replaced with other components. Further, the configuration elements whose arrangement is not particularly limited are not limited to the arrangement disclosed in the embodiments, but can be arranged at a position where the function can be achieved.

FIG. 1 is a diagram showing a camera including a lens barrel and a camera body according to a first embodiment. FIG. 2 is a cross-sectional view showing the relationship between the first lens holding frame and the second lens holding frame. FIG. 3 is a top view for explaining the engagement relationship between the first lens holding frame, the second lens holding frame, the internal fixing cylinder, and the cam ring. FIG. 4 is a partially sectional perspective view showing a part of the first lens holding frame, the second lens holding frame, the internal fixing cylinder, and the cam ring. FIG. 5(a) is a flowchart showing the processing of the control unit when starting up the camera, and FIG. 5(b) is a diagram showing a starting table. 3 is a flowchart showing normal processing. FIG. 6 is a diagram showing the detected value of the potentiometer, the detected value of the GMR sensor, the calculated Z-pos (zoom position) pulse, and the Z-pos (zoom position) when the zoom operation ring is rotated at a constant speed. . FIG. 8(a) is a graph showing changes in the detected value of the potentiometer and the detected value of the GMR sensor 60 in FIG. 7, and FIG. 8(b) is a graph showing changes in the Z-pos pulse and Z-pos in FIG. This is a graph showing. FIG. 3 is a diagram showing changes in the detected value of the potentiometer, the detected value of the GMR sensor, the Z-pos pulse, and the Z-pos when the user rotates the zoom operation ring in one direction and then reverses it. 10(a) is a graph showing changes in the detection value of the potentiometer in FIG. 9 and the detection value of the GMR sensor 60, and FIG. 10(b) is a graph showing the change in the Z-pos pulse and Z-pos in FIG. This is a graph showing. FIG. 6 is a diagram for explaining correction regarding a time delay in the output of a potentiometer.

Embodiments will be described below with reference to the drawings. FIG. 1 is a diagram showing a camera 103 including a lens barrel 100 and a camera body 101 according to the present embodiment. FIG. 2 is a sectional view showing the relationship between the first lens holding frame F1 and the second lens holding frame F2. FIG. 3 is a top view for explaining the engagement relationship between the first lens holding frame F1, the second lens holding frame F2, the internal fixing cylinder 11, and the cam ring 20. FIG. 4 is a partial cross-sectional perspective view showing a portion of the first lens holding frame F1, the second lens holding frame F2, the internal fixing cylinder 11, and the cam ring 20. As shown in FIG.

Note that in this embodiment, the lens barrel 100 is removable from the camera body 101, but the present invention is not limited to this, and the lens barrel 100 and the camera body 101 may be integrated.

As shown in FIG. 1, the lens barrel 100 according to the present embodiment includes a first lens group L1 and a second lens group L2 that are sequentially arranged along a common optical axis OA. Note that the lens barrel 100 may include other lens groups. The first lens group L1 is held by a first lens holding frame F1, and the second lens group L2 is held by a second lens holding frame F2. Note that in this embodiment, the first lens holding frame F1 and the second lens holding frame F2 hold the lens, but the first lens holding frame F1 and the second lens holding frame F2 may not hold the lens. good. Furthermore, in this embodiment, the second lens holding frame F2 is arranged on the outer peripheral side of the first lens holding frame F1, but the second lens holding frame F2 is arranged on the inner peripheral side of the first lens holding frame F1. may be placed.

The lens barrel 100 includes a fixed barrel 10. The fixed tube 10 has an inner fixed tube 11 and an outer fixed tube 12. As shown in FIG. 1, a lens mount 13 is fixed to the external fixed barrel 12 so that the lens barrel 100 can be attached to and detached from the camera body 101. As shown in FIGS. 1 and 3, the internal fixed cylinder 11 has a first straight groove 111 and a second straight groove 112.

Further, the lens barrel 100 includes a cam ring 20 on the inner circumferential side of the outer fixed barrel 12 and a zoom operation ring 30 on the outer circumferential side of the cam ring 20. The zoom operation ring 30 and the cam ring 20 are rotatable around the optical axis OA. The zoom operation ring 30 and the cam ring 20 are connected via a pin (not shown), so that the cam ring 20 rotates in conjunction with the rotation of the zoom operation ring 30. Note that the cam ring 20 may be rotationally driven by an actuator such as an ultrasonic motor. In that case, the motor rotates the cam ring 20 based on the amount of rotation of the zoom operation ring 30. As shown in FIGS. 1 and 3, the cam ring 20 has a first cam groove 21 and a second cam groove 22. As shown in FIGS.

As shown in FIGS. 1 and 3, a cam follower 51 that protrudes in a direction intersecting the optical axis OA direction is provided on the outer peripheral surface of the second lens holding frame F2. The cam follower 51 engages with the second linear groove 112 of the inner fixed cylinder 11 and the second cam groove 22 of the cam ring 20 . Thereby, when the cam ring 20 rotates in conjunction with the rotation of the zoom operation ring 30, the second lens holding frame F2 moves straight in the direction of the optical axis OA without rotating around the optical axis OA. Further, as shown in FIGS. 1, 3, and 4, the second lens holding frame F2 has a rectilinear groove 52 along the optical axis OA direction.

As shown in FIGS. 1, 3, and 4, a cam follower 41 that protrudes in a direction intersecting the optical axis OA direction is provided on the outer peripheral surface of the first lens holding frame F1. The cam follower 41 engages with the straight groove 52 of the second lens holding frame F2, the first straight groove 111 of the internal fixed cylinder 11, and the first cam groove 21 of the cam ring 20. Thereby, when the cam ring 20 rotates in conjunction with the rotation of the zoom operation ring 30, the first lens holding frame F1 moves straight in the direction of the optical axis OA without rotating around the optical axis OA. Note that the first rectilinear groove 111 of the internal fixed cylinder 11 is an escape groove.

The lens barrel 100 further includes a looseness removing spring 80, as shown in FIG. The backlash removing spring 80 is a tension spring, and one end is fixed to the first engagement part 42 provided on the outer peripheral surface of the first lens holding frame F1, and the other end is fixed to the engagement part provided on the second lens holding frame F2. It is fixed to the joining part 53. The engaging portion 53 of the second lens holding frame F2 is provided at a position facing the first engaging portion 42 of the first lens holding frame F1. Note that a plurality of backlash removing springs 80 (for example, three) are actually provided between the first lens holding frame F1 and the second lens holding frame F2.

By the looseness removing spring 80, the first lens holding frame F1 is pulled toward the second lens holding frame F2, as shown by arrow A1, and the second lens holding frame F2 is pulled toward the first lens holding frame F2, as shown by arrow A2. It is pulled toward the lens holding frame F1. As a result, the cam follower 41 of the first lens holding frame F1 and the cam follower 51 of the second lens holding frame F2 are pressed against the inner edges of the first cam groove 21 and the second cam groove 22 of the cam ring 20, respectively. Backlash when moving along the first cam groove 21 and the second cam groove 22 is prevented.

The lens barrel 100 according to the present embodiment includes a relative position detection section 60 and an absolute position detection section 70 as position detection mechanisms for the first lens group L1 and the second lens group L2.

The relative position detection unit 60 is, for example, a GMR (Giant Magneto Resistive effect) sensor. GMR sensors lose position information when powered off. In addition, below, the relative position detection part 60 is described as the GMR sensor 60.

As shown in FIGS. 1 and 3, the GMR sensor 60 includes a magnetic tape 61 and a GMR element 62. The magnetic tape 61 is provided on the outer peripheral surface of the cam ring 20 along the circumferential direction. The GMR element 62 is provided in a part of the external fixed cylinder 12. The GMR element 62 faces the magnetic tape 61, and sends a two-phase pulse train to the lens barrel according to the rotational position (position with respect to the external fixed barrel 12) and rotation amount around the optical axis OA of the cam ring 20. The output signal is output to a control unit (not shown) included in the control unit 100 . Thereby, from the output of the GMR element 62, the amount of movement (amount of rotation) and the direction of movement (rotation direction) of the cam ring 20 relative to the external fixed barrel 12 can be detected. Since the GMR sensor 60 with high resolution detects the amount of movement (amount of rotation) and direction of movement (rotation direction) of the cam ring 20 close to the zoom operation ring 30, the user's operation of the zoom operation ring 30 is detected at an early stage. becomes possible. Furthermore, since the GMR sensor 60 has a fast detection speed (there is no delay in detection), by arranging the GMR sensor 60 on the cam ring 20 near the zoom operation ring 30, the amount of movement (rotation amount) of the cam ring 20 can be adjusted. and the movement direction (rotation direction) can be quickly detected.

The absolute position detection section 70 is, for example, a potentiometer. Potentiometers do not lose their position information even when the power is turned off. Note that, hereinafter, the absolute position detection section 70 will be referred to as a potentiometer 70.

The potentiometer 70 is fixed to the second lens holding frame F2, as shown in FIGS. 1 and 4. The potentiometer 70 is a variable resistance whose resistance value continuously changes depending on the position of a protrusion (knob) 71 that is a movable contact. In this embodiment, the groove that engages with the knob 71 is installed along the optical axis OA direction. That is, in this embodiment, the potentiometer 70 is installed so that the knob 71 moves in the optical axis OA direction.

As shown in FIG. 1, the first lens holding frame F1 includes a second engaging portion 43 extending from the first lens holding frame F1 toward the second lens holding frame F2, and the knob 71 of the potentiometer 70 is , fits into the hole 43a formed in the second engaging portion 43. Thereby, when the first lens holding frame F1 moves straight in the optical axis OA direction, the knob 71 moves in the optical axis OA direction in conjunction with the movement of the first lens holding frame F1, and the resistance value changes. The control unit included in the lens barrel 100 can acquire the resistance value from the potentiometer 70 and use the resistance value to measure the position of the first lens holding frame F1 with respect to the second lens holding frame F2.

Here, since the potentiometer 70 is fixed to the second lens holding frame F2, the position of the first lens holding frame F1 with respect to the second lens holding frame F2 can be detected from the output of the potentiometer 70. The position of the first lens holding frame F1 with respect to the second lens holding frame F2 (hereinafter simply referred to as the lens position) changes in accordance with the change in the distance between the first lens group L1 and the second lens group L2. Change. That is, the lens position changes depending on the zoom position of the lens barrel 100. Conversely, the control unit can determine the zoom position of the lens barrel 100 from the detected lens position.

A method of detecting the zoom position using the potentiometer 70 and the GMR sensor 60 in the lens barrel 100 configured as described above will be described.

In this embodiment, when the user performs a zoom operation via the zoom operation ring 30 after the camera body 101 is powered on, the control unit controls the rotation of the cam ring 20 based on the output of the GMR sensor 60. To detect. Then, when the detected value is output from the potentiometer 70, the control section detects the zoom position (lens position) based on the detected value of the potentiometer 70 and the detected value of the GMR sensor 60. After that, the lens position is detected using the output pulse (GMR pulse position) of the GMR sensor 60.

In the following, the processing of the control unit when the camera body 101 is powered on (at startup) and the processing of the control unit during normal times will be described in detail.

(Processing at startup)
FIG. 5A shows a flowchart of the processing of the control unit when the camera 103 (camera body 101) is activated. Note that although it has been described above that the lens barrel 100 includes the control unit, the control unit included in the camera body 101 may execute the processing. As a premise of the process shown in FIG. 5A, the non-volatile memory (not shown) possessed by the control unit stores the detected value of the potentiometer 70 obtained immediately before the last power-off, the zoom position, the GMR pulse position, and the zoom operation. It is assumed that the rotation direction of the ring 30 is stored. Note that the time of startup also includes the time of return from a sleep state.

In the process of FIG. 5A, first, in step S10, the control unit reads the detected value of the potentiometer 70 before the power is turned off from the nonvolatile memory.

Next, in step S12, the control unit reads the current detection value of the potentiometer 70.

Next, in step S14, the control unit determines whether the difference between the value before the power is turned off and the current value is less than or equal to a predetermined value. If the determination in step S14 is negative (if the difference is greater than a predetermined value), the process moves to step S16.

In step S16, the control section determines the zoom position and GMR pulse position from the value of the potentiometer 70. At this time, the control unit refers to the startup table shown in FIG. 5(b). The startup table in FIG. 5B stores the zoom position (Z-pos) and the GMR pulse position in association with the value of the potentiometer 70. By using this start-up table, appropriate values can be determined as the initial values of the zoom position and the GMR pulse position based on the value of the potentiometer 70 obtained at the time of start-up.

On the other hand, if the determination in step S14 is affirmative (if the difference is less than or equal to the predetermined value), the process moves to step S18, and the control unit stores the zoom position, GMR pulse position, and direction before power OFF from the nonvolatile memory. Read and restore (set as initial value). In this way, in step S18, by inheriting the zoom position etc. before the power was turned off, the zoom position may change slightly even though the user did not intend to operate the zoom operation ring 30 between the time the power was turned off and turned on. This can prevent the user from feeling unnatural.

After the process of step S16 or S18 is performed, the entire process of FIG. 5(a) ends.

(Normal processing)
Next, normal processing will be explained along the flowchart of FIG. 6.

In the process of FIG. 6, first, in step S30, the control unit determines whether the GMR pulse (output of the GMR sensor 60) has changed by a threshold value or more after calculating the previous zoom position. While the determination in step S30 is negative, the control unit repeatedly executes step S30. On the other hand, if the determination in step S30 is affirmative, the process moves to step S32.

When proceeding to step S32, the control unit determines based on the output of the GMR sensor 60 whether the zoom operation ring 30 is being operated (rotated) in the same direction as when the zoom position was calculated last time.

If the determination in step S32 is affirmative, the process moves to step S34, and the control section calculates the zoom position from the output of the GMR sensor 60 (GMR pulse position). After that, the process returns to step S30.

On the other hand, if the determination in step S32 is negative, that is, if the user operates the zoom operation ring 30 in the opposite direction to the direction in which the zoom position was calculated last time, the process moves to step S36, and the control unit determines whether the output value of the potentiometer 70 has changed by more than a threshold value since the previous zoom position calculation. If the determination at step S36 is negative, the process returns to step S30, but if the determination is affirmative, the process moves to step S38.

In step S38, the control section determines the zoom position and GMR pulse position from the value of the potentiometer 70. That is, the same process as step S16 described above is performed. After that, the process returns to step S30.

Note that, before returning to step S30, the control section transmits zoom position information to the control section of the camera body 101 (body-side control section) via the communication section. That is, in this embodiment, the control section transmits correction information (zoom position) obtained by correcting the detection value of the GMR sensor 60 with the detection value of the potentiometer 70 to the body-side control section via the communication section. Here, the body-side control section executes various controls such as changing the aperture and shutter speed based on the received zoom position. Furthermore, the control unit executes zoom tracking by controlling a motor that drives a focus lens within the lens barrel 100 based on the zoom position. Zoom tracking is an electrical position correction operation of the focus lens to maintain the focus position even if the focal length is changed.

Here, as an example, a process will be described in which the zoom operation ring 30 is rotated at a constant speed from the wide end to the tele end after starting up the camera 103 (camera body 101). In this case, as shown in FIG. 7, it is assumed that the detection value of the potentiometer 70 and the detection value (GMR pulse position) of the GMR sensor 60 are output to the control section.

FIG. 8(a) shows changes in the detection value of the potentiometer 70 and the detection value (GMR pulse position) of the GMR sensor 60 in FIG. 7. In FIG. 8(a), the horizontal axis shows time and the vertical axis shows detected values. When the user starts rotating the zoom operation ring 30, the detected value (GMR pulse position) of the GMR sensor 60 starts to change (see arrow A). At this time, step S30 (affirmative), step S32 (negative), and step S36 (negative) are repeated, and when the value of the potentiometer 70 changes by a threshold value (for example, "1") or more (see arrow B), the determination in step S36 is If affirmative, the process moves to step S38. Then, in step S38, the control section determines the zoom position using the value of the potentiometer 70 and the GMR pulse position. Specifically, at the time indicated by arrow B, the value of the potentiometer 70 is 1, so the value "13" of the GMR pulse position is changed to a value corresponding to the value "1" of the potentiometer 70 (for example, " 1)). This corrected pulse is called a Z-pos pulse.

FIG. 8(b) shows the Z-pos pulse in FIG. 7 and changes in Z-pos. As shown in FIG. 8(b), at the time point indicated by arrow C, the Z-pos pulse indicates "1". From then on, the control unit similarly corrects the detected value (GMR pulse position) of the GMR sensor 60 to obtain the Z-pos pulse (step S34). Further, the control unit calculates Z-pos (zoom position) from the obtained Z-pos pulse (step S34). Note that in FIG. 8B, Z-pos is set to 1 when the Z-pos pulses are 1 to 6, and Z-pos is set to 2 when the Z-pos pulses are from 7 to 12. Thereafter, every time the number of Z-pos pulses increases by 6, the control unit increases Z-pos by 1.

Next, the processing of the control unit when the user reverses the zoom operation ring 30 will be described. FIG. 9 shows the detected value of the potentiometer 70, the detected value of the GMR sensor 60, the Z-pos pulse, and the transition of Z-pos when the user rotates the zoom operation ring 30 in one direction and then reverses it. It is shown. Further, FIG. 10(a) shows changes in the detected values of the potentiometer 70 and the GMR sensor 60.

When the user starts reversing the zoom operation ring 30, the GMR sensor 60 detects a change in direction, as shown by arrow D in FIG. 10(a). On the other hand, in the potentiometer 70, the reversal is detected with a delay (see arrow E). In this case, when the change in the value of the potentiometer 70 indicated by the arrow E appears, the determination in step S36 in FIG. 6 is affirmed, so the control section moves to step S38. In step S38, the control unit determines the Z-pos pulse at the time of inversion, as shown by the double-headed arrow F in FIG. 10(b). By doing so, the control section can appropriately determine the Z-pos pulse even when the zoom operation ring 30 is reversed. Further, even after the inversion, the control unit can accurately calculate the zoom position using the Z-pos pulse.

As described above, when the detection values of the potentiometer 70 and the GMR sensor 60 both change, the control unit determines that the zoom position has changed. This prevents deviations between changes in the detected value and changes in the zoom position due to play, etc., and enables precise control.

(Correction regarding time delay)
The control unit periodically performs A/D conversion on the output of the potentiometer 70 to obtain an AD value, and uses a moving average to average a plurality of results and sets the value detected by the potentiometer 70 as the detected value. By doing so, the influence of fluctuations in the AD value is suppressed. Because such processing is performed, there is a time delay in the output of the potentiometer 70.

For example, when taking a moving average of the past 8 AD values obtained every 500 μs, the moving average from the AD value obtained 3500 μs ago to the latest AD value is calculated as shown in Figure 11. The center of gravity of is located between 1500 μs and 2000 μs. When moving at a constant speed, there is a delay of 1750 μs. In this case, the value output as the latest output value means the value 1750 μs ago.

On the other hand, the GMR sensor 60 has no delay. Therefore, when calculating the GMR pulse position from the AD value of the potentiometer 70, the delay can be corrected by adding the number of pulses by the delay equivalent to 1750 μs.

Note that the correction amount does not necessarily have to match the theoretical moving average delay time, and a larger number of pulses may be added in consideration of the delay on the driving side. Conversely, a smaller number of pulses may be added to prevent excessive control.

In this case, the correction amount may be adjusted by using the history to determine whether the vehicle is accelerating or decelerating. For example, divide the history of 8 times into 4 times from the latest to 3 times ago, and 4 times from the 4th time to the 7th time ago, calculate the GMR pulse speed for each, and determine whether it is accelerating or decelerating. It is also possible to determine whether there is a correction amount and determine the amount of correction.

Note that the GMR pulse speed is calculated by dividing the difference between the past value and the current value by time. Here, how much of the past value is used as the past value changes depending on the speed at which the user rotates the zoom operation ring 30.

When the user operates the zoom operation ring 30 at a high speed, a large number of pulses are generated, so that an accurate GMR pulse speed can be calculated even from the number of pulses for a short period of time. During such high-speed rotation, it is convenient to calculate the speed from the number of short-term pulses, including the purpose of increasing responsiveness.

On the other hand, if the user operates the zoom operation ring 30 at a low speed, the number of pulses obtained in a short period of time is small, making it impossible to calculate an accurate GMR pulse speed. Also, the slower the operation, the less important it is to increase responsiveness.

In this embodiment, the control unit calculates the GMR pulse speed by dividing the operation speed of the zoom operation ring 30 into multiple (for example, three) speed ranges.

for example,
(1) “Ultra high speed” that calculates speed immediately in a short time
(2) "High speed" which is the speed range between ultra high speed and normal speed
(3) "Normal" where the speed is calculated accurately using the GMR pulse speed obtained a relatively long time ago
The control unit determines the GMR pulse speed to be adopted in the priority order of (3)→(2)→(1) from among the respective calculation results.

Note that a plurality of GMR pulse velocities may be calculated at previous and subsequent times, and based on this, an acceleration tendency or a deceleration tendency may be determined, and the determination result may be reflected in the correction amount.

Note that if the zoom operation ring 30 is operated slowly to a certain extent, the delay correction is no longer important, so the delay correction may not be performed when the operation speed of the zoom operation ring 30 falls below a certain degree.

In the present embodiment, a case has been described in which the control section on the side of the lens barrel 100 obtains the Z-pos pulse, calculates the zoom position based on this, and transmits it to the control section on the body side. However, the present invention is not limited to this, and the control unit on the lens barrel 100 side may obtain the Z-pos pulse and transmit it to the body side control unit. In this case, the body side control section may calculate the zoom position and transmit it to the lens barrel 100 side control section.

As described above in detail, according to the present embodiment, the lens barrel 100 includes the cam ring 20, the outer fixed barrel 12 disposed on the outer peripheral side of the cam ring 20, the cam ring 20 and the outer fixed barrel. 12, the first lens holding frame F1, the second lens holding frame F2 placed on the outer circumferential side of the first lens holding frame F1, and the first lens holding frame F1 and the first lens holding frame F1. and a potentiometer 70 disposed between the two lens holding frames F2.

When both the GMR sensor 60 and the potentiometer 70 are arranged between the cam ring 20 and the external fixed cylinder 12, the lens position is determined only by the positional relationship between the cam ring 20 and the external fixed cylinder 12. Become. In this embodiment, the GMR sensor 60 determines the lens position based on both the positional relationship between the cam ring 20 and the external fixed barrel 12, and the positional relationship between the first lens holding frame F1 and the second lens holding frame F2. This improves the accuracy of lens position detection. Further, even if a shift occurs in the positional relationship between the cam ring 20 and the external fixed cylinder 12 due to aging or the like, the detection value of the GMR sensor 60 can be supplemented using the detection result of the potentiometer 70. On the contrary, even if a shift occurs in the positional relationship between the first lens holding frame F1 and the second lens holding frame F2 due to deterioration over time, etc., the detected value of the potentiometer 70 can be supplemented using the detection result of the GMR sensor 60. Can be done.

Further, according to the present embodiment, the external fixing cylinder 12 and the cam ring 20 are arranged on the outer peripheral side of the first lens holding frame F1 and the second lens holding frame F2. A GMR sensor 60 having a higher resolution than the potentiometer 70 is provided at a position close to the zoom operation ring 30 on the path until the rotational operation of the zoom operation ring 30 is transmitted to the first lens holding frame F1 and the second lens holding frame F2. In this way, it is possible to detect at an early stage that the user has operated the zoom operation ring 30.

Further, according to the present embodiment, the first lens holding frame F1 and the second lens holding frame F2 hold the first lens group L1 and the second lens group L2, respectively. Since the position of the first lens group L1 can be directly detected by the potentiometer 70, the detection accuracy of the lens position can be improved.

Further, according to the present embodiment, the first lens holding frame F1 and the second lens holding frame F2 are movable in the optical axis OA direction, and the first lens holding frame F1 is movable in the direction of the optical axis OA. It is movable relative to the In the case of this configuration, it is sufficient to detect the difference in the amount of movement between the first lens holding frame F1 and the second lens holding frame F2, so the potentiometer 70 can be made smaller.

Further, according to the present embodiment, the looseness removing spring 80 is disposed between the first lens holding frame F1 and the second lens holding frame F2. The backlash removing spring 80 pulls the first lens holding frame F1 toward the second lens holding frame F2, and the second lens holding frame F2 is pulled toward the first lens holding frame F1. As a result, the cam follower 41 of the first lens holding frame F1 and the cam follower 51 of the second lens holding frame F2 are pressed against the inner edges of the first cam groove 21 and the second cam groove 22 of the cam ring 20, respectively. Backlash when moving along the first cam groove 21 and the second cam groove 22 is prevented.

Further, according to the present embodiment, the control unit acquires the detection value of the potentiometer 70 and the detection value of the GMR sensor 60, and provides correction information (zoom position ) is sent to the body-side control unit. Thereby, the time delay in the output of the potentiometer 70 can be appropriately corrected. Furthermore, the body-side control unit can accurately perform various controls such as changing the aperture and shutter speed based on the received zoom position.

Further, according to the present embodiment, the control unit performs zoom tracking by controlling the motor that drives the focus lens in the lens barrel 100 based on the correction information (zoom position). can be performed with high precision.

In addition, in the said embodiment, although the GMR sensor 60 was demonstrated as an example as a relative position detection part, it is not restricted to this. Instead of the GMR sensor 60, for example, another sensor such as a magnetic encoder or an optical encoder may be used.

Further, in the above embodiment, a case has been described in which the magnetic tape 61 of the GMR sensor 60 is provided on the cam ring 20 and the GMR element 62 is provided on the external fixed cylinder 12, but the present invention is not limited to this. The magnetic tape 61 may be provided on the external fixed cylinder 12 and the GMR element 62 may be provided on the cam ring 20. Further, the GMR element 62 may be provided in a part of the inner fixed cylinder 11, and the magnetic tape 61 may be provided on the inner peripheral surface of the cam ring 20 disposed on the outer peripheral side of the inner fixed cylinder 11. Alternatively, the magnetic tape 61 may be provided on the outer circumferential surface of the internal fixed cylinder 11 and the GMR element 62 may be provided on the cam ring 20.

Furthermore, in the embodiment described above, the potentiometer 70 is used as an example of the absolute position detecting section, but the present invention is not limited to this. Any sensor that does not lose position information even when the power is turned off may be used, and instead of the potentiometer 70, for example, an encoder using a code plate may be used.

Further, in the above embodiment, the potentiometer 70 is provided in the second lens holding frame F2, but it may be provided in the first lens holding frame F1. In this case, the second lens holding frame F2 only needs to have an engaging portion that engages with the knob 71 of the potentiometer 70.

Moreover, in the embodiment described above, the first lens holding frame F1 or the second lens holding frame F2 may be a fixed cylinder. In this case, the first lens holding frame F1 or the second lens holding frame F2, which are fixed cylinders, may be integrated with the inner fixed cylinder 11 or the outer fixed cylinder 12, or may be separate bodies.

In the above embodiment, the control unit included in the lens barrel 100 controls the zoom position and GMR pulse from the value of the potentiometer 70 when the camera 103 (camera body 101) is started and when the operation (rotation) direction of the zoom operation ring 30 is reversed. Although the process of determining the position is performed, for example, if the value of the potentiometer 70 and the value of the potentiometer 70 obtained by back calculation from the value of the Z-pos pulse deviate by more than a predetermined value, the potentiometer 70 Processing may be performed to determine the zoom position and GMR pulse position from the value of .

Note that even when both the GMR sensor 60 and the potentiometer 70 are arranged between the cam ring 20 and the external fixed barrel 12, the zoom position detection method according to the above embodiment can be applied.

The embodiments described above are examples of preferred implementations. However, the present invention is not limited to this, and various modifications can be made without departing from the spirit of the invention, and arbitrary constituent elements may be combined.

11 Inner fixed barrel 12 Outer fixed barrel 20 Cam ring 21 First cam groove 22 Second cam groove 30 Zoom operation ring 41 Cam follower 51 Cam follower 52 Straight groove 60 GMR sensor 61 Magnetic tape 62 GMR element 70 Potentiometer L1 First lens group L2 2nd lens group F1 1st lens holding frame F2 2nd lens holding frame 100 Lens barrel 101 Camera body 103 Camera 111 1st straight groove 112 2nd straight groove

Claims (16)

The first cylinder and
a second cylinder disposed on the inner circumferential side or the outer circumferential side of the first cylinder;
a first detection unit that detects a relative position of the second cylinder with respect to the first cylinder;
The third cylinder and
a fourth cylinder disposed on the inner circumferential side or the outer circumferential side of the third cylinder;
a second detection unit that detects the absolute position of the fourth cylinder with respect to the third cylinder;
a control unit that detects a change in focal length based on the first detection unit and the second detection unit;
A position detection mechanism comprising: The position detection mechanism according to claim 1, wherein the accuracy of the first detection section is higher than the accuracy of the second detection section. 3. The position detection mechanism according to claim 1, wherein the first detection section outputs a pulse train, and the second detection section outputs a continuously changing value. The position detection mechanism according to any one of claims 1 to 3, wherein the detection result of the second detection section is corrected based on the detection result of the first detection section. The control unit is configured such that the first detection unit detects relative movement between the first cylinder and the second cylinder, and the second detection unit detects relative movement between the third cylinder and the fourth cylinder. The position detection mechanism according to any one of claims 1 to 4, wherein it is determined that the focal length has changed when a certain movement is detected. The second detection unit detects relative movement between the third cylinder and the fourth cylinder after the first detection unit detects the relative movement between the first cylinder and the second cylinder. do,
The position detection mechanism according to claim 5 . The first detection section has a detection element and a detected part, the detection element is arranged in one of the first cylinder and the second cylinder, and the detected part is arranged in one of the first cylinder and the second cylinder. Placed on the other side of the two cylinders,
The position detection mechanism according to any one of claims 1 to 6 . The second detection unit is arranged in one of the third cylinder and the fourth cylinder,
The position detection mechanism according to any one of claims 1 to 7 . The first cylinder and the second cylinder are arranged on the outer peripheral side of the third cylinder and the fourth cylinder,
The position detection mechanism according to any one of claims 1 to 8 . an optical system having a plurality of lenses, the focal length of which changes by changing the distance between the lenses;
The position detection mechanism according to any one of claims 1 to 9,
A lens barrel in which a driving force for changing the focal length is transmitted to at least one of the first barrel and the second barrel, and then transmitted to at least one of the third barrel and the fourth barrel. Equipped with a removable lens mount on the camera body,
When the focal length changes, the third cylinder and the fourth cylinder move in the optical axis direction with respect to the lens mount, and the distance between the third cylinder and the fourth cylinder also changes. Item 10. The lens barrel according to item 10. The lens barrel according to claim 10 or 11, further comprising a biasing member disposed between the third barrel and the fourth barrel. The fourth cylinder has a first cam follower that engages with a first cam groove of the first cylinder and a straight groove of the second cylinder,
The third cylinder has a second cam follower that engages with a second cam groove of the first cylinder and a straight groove of the fourth cylinder.
The lens barrel according to any one of claims 10 to 12 . The position detection mechanism includes a communication unit that transmits the change in focal length detected by the control unit to the camera body.
The lens barrel according to any one of claims 10 to 13 . The position detection mechanism includes a drive unit that drives the lens,
The control unit controls the drive unit based on the detected change in the focal length .
The lens barrel according to any one of claims 10 to 13 . An optical device comprising the lens barrel according to any one of claims 10 to 15 .

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