JP5440239B2 - Movement amount detection device, lens unit, and imaging device - Google Patents

Description

  The present invention relates to a movement amount detection device, a lens unit, and an imaging device.

As a device for detecting the amount of rotation of the cam ring included in the lens unit, a device that calculates the amount of rotation of the cam ring from the amount of rotation of a rotating disk arranged coaxially with a gear that transmits drive from the motor to the cam ring is known. (For example, refer to Patent Document 1). In this apparatus, there is a time difference between the start of pulse generation by the encoder and the start of rotation of the cam ring due to the influence of backlash such as gear backlash. Thereby, an error occurs in the rotation amount of the rotating body.
[Prior art documents]
[Patent Literature]
[Patent Document 1] Japanese Patent Application Laid-Open No. 2006-258586

  In view of the above circumstances, an object of the present invention is to provide a movement amount detection device that can improve the detection accuracy of the movement amount of a moving body.

  In order to solve the above problems, in the first aspect of the present invention, a pulse signal output unit (130) that outputs a pulse signal as the actuator (114) that moves the moving body (210) is driven; The pulse detection unit (220) that detects the acceleration of the moving body, and the acceleration detection unit that detects the acceleration indicating that the moving body has started to move, are output from the pulse signal output unit. There is provided a movement amount detection device (100) comprising a movement amount calculation unit (112) that calculates a movement amount of the moving body by counting pulse signals.

  It should be noted that the above summary of the invention does not enumerate all the necessary features of the present invention. In addition, a sub-combination of these feature groups can also be an invention.

It is a figure which shows schematic structure of a digital camera provided with the movement amount detection apparatus 100 which concerns on one Embodiment. It is a perspective view which shows the cam ring 210, the motor 114, and the encoder 130. FIG. 3 is a block diagram showing a circuit configuration of an acceleration sensor 220. FIG. It is a graph showing the characteristics of sensor output V ₀ which the acceleration sensor 220. 3 is a graph showing the relationship between the number of pulses output from an encoder 130 and the amount of rotation of a cam ring 210. 4 is a flowchart for explaining a method of detecting the amount of rotation of a cam ring 210 in the movement amount detection device 100.

  Hereinafter, the present invention will be described through embodiments of the invention, but the following embodiments do not limit the invention according to the claims. In addition, not all the combinations of features described in the embodiments are essential for the solving means of the invention.

  FIG. 1 is a diagram illustrating a schematic configuration of a digital camera including a movement amount detection device 100 according to an embodiment. As shown in this figure, the digital camera includes a camera body 110 and a lens unit 200. The camera body 110 includes a microcomputer unit (hereinafter referred to as MCU 112), a motor 114, a motor drive circuit 116 that drives the motor 114, and a gear train 118 that transmits the driving force of the motor 114. . The MCU 112, the motor 114, the motor drive circuit 116, and the gear train 118 are arranged in the camera body 110 in this embodiment, but these may be arranged in the lens unit 200.

  The lens unit 200 includes a photographing lens 202, a lens frame 204 that holds the photographing lens 202, a cam ring 210 that moves the lens frame 204 in the optical axis direction of the photographing lens 202, and an acceleration sensor 220 disposed on the cam ring 210. And. The cam ring 210 includes a cam portion 214 in which a cam groove 212 is formed, and a drive portion 216 that can relatively move the cam portion 214 in the optical axis direction and that can rotate integrally around the optical axis. A cam follower 218 protruding from the lens frame 204 is inserted into the cam groove 212, and the cam follower 218 is pushed from the cam groove 212 by the rotation of the cam portion 214, so that the lens frame 204 moves in the optical axis direction. To do.

  In addition, a rack 222 is formed in the drive unit 216 along the circumferential direction. The rack 222 meshes with the gear 119 of the gear train 118. Therefore, the driving force of the motor 114 is transmitted to the rack 222 via the gear train 118, and the driving unit 216 and the cam unit 214 are rotated around the optical axis.

  The driving unit 216 is provided with an acceleration sensor 220. The acceleration sensor 220 detects the acceleration of the drive unit 216 and outputs a detection signal to the MCU 112 when the drive unit 216 rotates.

  The camera body 110 includes a relative encoder 130. The encoder 130 includes a rotating disk 132 that is arranged coaxially with one gear included in the gear train 118 and rotates together with the gear, and an optical sensor 134. On the outer periphery of the rotating disk 132, coded opaque sectors and transparent sector patterns are formed. Further, the optical sensor 134 includes a light emitting unit and a light receiving unit that face each other with the outer peripheral portion of the rotating disk 132 interposed therebetween. When the rotating disk 132 is rotated, the light beam emitted from the light emitting unit to the light receiving unit of the optical sensor 134 is blocked by the opaque sector of the pattern and transmitted by the transparent sector. The corresponding pulse signal is output.

  FIG. 2 is a perspective view showing the cam ring 210, the motor 114, and the encoder 130. As shown in this figure, the gear train 118 includes a two-stage gear 122 that meshes with the pinion gear 120 of the motor 114 and the large gear, and a gear 124 that meshes with the small gear of the two-stage gear 122. A rotating disk 132 is fixed to the rotating shaft of the gear 124, and the gear 124 and the rotating disk 132 rotate integrally around the same axis.

  Here, since the scale of the encoder 130 is the rotating disk 132 fixed to the rotating shaft of the gear 124, the scale can be reduced in size and simplified as compared with the case where the scale is directly arranged on the cam ring 210. Therefore, the cost of the movement amount detection device 100 can be reduced and the configuration of the movement amount detection device 100 can be simplified.

  The acceleration sensor 220 is disposed on the outer peripheral portion of the drive unit 216. The acceleration sensor 220 may be disposed on the inner peripheral portion of the driving unit 216 or may be disposed on the cam unit 214. The acceleration sensor 20 detects the tangential acceleration of the rotational motion of the drive unit 216.

FIG. 3 is a block diagram showing a circuit configuration of the acceleration sensor 220. As shown in this figure, the acceleration sensor 220 outputs a sensor output V ₀ and a sensor reference voltage V _ref for designating a reference value of the sensor output V ₀ to a low-pass filter (hereinafter referred to as LPF 224). The LPF 224 includes resistors 226 and 228, capacitors 230 and 232, and an operational amplifier 234. The LPF 224 removes high frequency noise input to the acceleration sensor 220 and stabilizes the sensor output V ₀ .

The addition amplifier unit 236 includes resistors 238, 240, 242, an operational amplifier 244, and a capacitor 246. The addition amplifier unit 236 applies a gain to the sensor output V ₀ stabilized by the LPF 224 and outputs the gain to the AD converter (hereinafter referred to as ADC 248) of the MCU 112.

The MCU 112 is provided with a DA converter (hereinafter referred to as DAC 250). The DAC 250 performs initial adjustment of the sensor output V ₀ so that the voltage becomes the sensor reference voltage V _ref by applying a voltage to the adding amplifier unit 236.

FIG. 4 is a graph showing the characteristics of the sensor output V ₀ of the acceleration sensor 220. As shown in this graph, the acceleration sensor 220 outputs the sensor reference voltage V _ref in the initial state. When the cam ring 210 rotates in one direction (for example, clockwise when viewed from the subject side), the acceleration sensor 220 outputs a positive voltage with respect to the sensor reference voltage V _{ref as} indicated by a solid line in the graph. ,To accelerate. The sensor reference voltage V _ref is output at a constant speed, and a negative voltage is output with respect to the reference voltage V _ref during deceleration.

On the other hand, when the cam ring 210 rotates in the other direction (for example, counterclockwise when viewed from the subject side), the acceleration sensor 220 has a negative voltage with respect to the sensor reference voltage V _{ref as} indicated by a broken line in the graph. Is output. That is, the output profile is the reverse of that when the cam ring 210 rotates in the one direction. When the cam ring 210 rotates, the sensor output V ₀ increases or decreases from the initial state and goes through a transient state, and then becomes a constant value V _ref . Further, when the rotation of the cam ring 210 stops, the sensor output V ₀ decreases or increases after passing through a transient state to become the sensor reference voltage V _ref .

Here, threshold values V ₁ (≠ 0) and V ₋₁ (≠ 0) for detecting that the cam ring 210 is started and stopped are set in advance. Threshold _{V 1} was, is set to an intermediate value between the sensor reference voltage _{V ref} and _{V cw,} the threshold _{V -1} is set to an intermediate value between the sensor reference voltage _{V ref} and _{V ccw.} V _cw, V _ccw, the upper limit value of the acceleration that is set in the displacement detection apparatus 100 of the present embodiment is a sensor output value corresponding to the lower limit value.

FIG. 5 is a graph showing the relationship between the number N of pulses output from the encoder 130 and the rotation amount M of the cam ring 210. When there is no backlash or other backlash in the engagement of the pinion gear 120, the gear train 118, and the rack 222, a pulse is output from the encoder 130 simultaneously with the start of the cam ring 210, as indicated by a solid line in this graph. On the other hand, in actuality, since there is a backlash or other play in the engagement of the pinion gear 120, the gear train 118, and the rack 222, as indicated by the chain line in this graph, the motor 114 is started. Until the cam ring 210 is started, a pulse of N ₀ is output. For this reason, the error M _{0 corresponding} to the pulse number N ₀ is added to the rotation amount of the cam ring 210. That is, while the exact rotation amount of the cam ring 210 is M, the rotation amount measured of the cam ring 210 is M + M ₀ .

  Further, when the rotation of the cam ring 210 is stopped, after the driving of the motor 114 is stopped, the cam ring 210 is rotated by the amount of gear play. For this reason, an error due to gear play is insufficient with respect to the accurate rotation amount of the cam ring 210.

FIG. 6 is a flowchart for explaining a method for detecting the amount of rotation of the cam ring 210 in the movement amount detection apparatus 100. As shown in this flowchart, in this processing routine, first, in step S100, the acceleration sensor 220 outputs a sensor reference voltage _Vref . Next, in step S102, MCU 112 is, the sensor output _{V 0} which the acceleration sensor 220, the threshold value _{V -1} or less, or, whether it is a _{V 1} or more. If the determination is negative, step S102 is repeatedly executed. If the determination is affirmative, the process proceeds to step S104.

In step S104, the MCU 112 starts counting the pulses output from the encoder 130, and proceeds to step S106. In step S106, it determines MCU112 is, the sensor output _{V 0} which acceleration sensor 220 is the threshold value _{V -1} or more, or, whether it is a _{V 1} below. In this case, if the sensor output V ₀ which the acceleration sensor 220 has been determined that the threshold value V ₁ or more in the above step S102, is accelerated and decelerated by the solid line profile in FIG. Therefore in this case, the sensor output V ₀ after step S102 through the time of the threshold value V ₁ or less, the time when the V _-1 or less in this order, then, through the time when the threshold V _-1 or more. Therefore, when the sensor output _{V 0} which the acceleration sensor 220 has been determined that the threshold value _{V 1} or more at step 102, in step S106, when the sensor output _{V 0} is the threshold value _{V 1} or _less, and _{V -1} or less After a certain point in time, it is determined whether or not the threshold value V ₋₁ is reached.

On the other hand, when the sensor output V ₀ of the acceleration sensor 220 is determined to be equal to or less than the threshold value V _{−1 in} step S102, acceleration and deceleration are performed with the broken line profile in FIG. Therefore in this case, the sensor output V ₀ after the step S102 through the time of the threshold value V _-1 or more, the time at which the V ₁ or more in this order, then, through the time when the threshold value V ₁ or less. Therefore, when the sensor output _{V 0} which the acceleration sensor 220 has been determined that the threshold value _{V -1} or less at step 102, in step S106, when the sensor output _{V 0} is the threshold value _{V -1} or more, _{V 1} or more after passing through the point at which a determines whether it is the threshold value V ₁ or less.

These determinations are performed, for example, by the MCU 112 counting the number of times the sensor output V ₀ has exceeded the threshold value V ₁ or V ₋₁ based on the output from the acceleration sensor 220 and storing it in the memory. . If the determination is negative, step S106 is repeatedly executed. If the determination is affirmative, the process proceeds to step S108.

  In step S108, the MCU 112 stops counting the pulses output from the encoder 130, and calculates the rotation amount of the cam ring 210 from the count value of the number of pulses. This processing routine is completed above.

Here, in the present embodiment, the fact that the cam ring 210 has started to rotate is detected by the acceleration sensor 220 disposed on the cam ring 210. The MCU 112 does not count the pulses output from the encoder 130 as the motor 114 is driven until the acceleration sensor 220 detects that the cam ring 210 has started to rotate. The MCU 112 starts counting the pulses output from the encoder 130 after the acceleration sensor 220 detects that the cam ring 210 has started to rotate. As a result, the error M _{0 corresponding} to the number of pulses N ₀ due to gear play is removed from the calculation result of the rotation amount of the cam ring 210 by the MCU 112. Therefore, in the configuration in which the rotary disk 132 as the measuring element of the encoder 130 is arranged at a position away from the cam ring 210 as the measurement target, the play is caused by play in the drive transmission mechanism between the motor 114 and the cam ring 210. The measurement error of the rotation amount of the cam ring 210 can be suppressed.

  In the present embodiment, the acceleration sensor 220 detects that the rotation of the cam ring 210 has stopped. The MCU 112 continues to count pulses output from the encoder 130 until the acceleration sensor 220 detects that the cam ring 210 is stopped. The MCU 112 stops counting the pulses output from the encoder 130 after the acceleration sensor 220 detects that the rotation of the cam ring 210 has stopped. Thereby, an error corresponding to gear play is removed from the calculation result of the amount by which the MCU 112 rotates until the cam ring 210 stops. Therefore, in the configuration in which the rotary disk 132 as the measuring element of the encoder 130 is arranged at a position away from the cam ring 210 as the measurement target, the play is caused by play in the drive transmission mechanism between the motor 114 and the cam ring 210. The measurement error of the amount of rotation until the cam ring 210 is stopped can be suppressed.

  In this embodiment, the rotating disk 132 is fixed to the rotating shaft of the gear 124 included in the gear train 118 that transmits the drive from the motor 114 to the cam ring 210. A two-stage gear 122 as a reduction gear is disposed between the gear 124 and the pinion gear 120 of the motor 114. Thereby, compared with the case where the rotating disk 132 is fixed to the rotating shaft of the motor 114, the rotating speed of the rotating disk 132 can be reduced, and the resolution of the output pulse of the encoder 130 can be improved.

  It is not essential that the rotating disk 132 be arranged coaxially with one gear included in the gear train 118, and the rotating disk 132 may be arranged coaxially with the rotating shaft of the motor 114. In this case, since no gear is interposed between the motor 114 and the rotary disk 132, the measurement accuracy of the rotation amount of the rotary disk 132 can be improved.

As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above-described embodiment. It is apparent from the scope of the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention. For example, in the above-described embodiment, the measurement target of the movement amount detection device 100 is a cam ring as a rotating body, but the measurement target may be a moving body that moves linearly, such as the lens frame 204. . The threshold value V ₁ (−V ₁ ) indicating that the rotation of the cam ring 210 has stopped is not necessarily the same as the threshold value indicating that the rotation of the cam ring 210 has started, and is a different value. Also good.

  The order of execution of each process such as operations, procedures, steps, and stages in the apparatus, system, program, and method shown in the claims, the description, and the drawings is particularly “before” or “prior to”. It should be noted that the output can be realized in any order unless the output of the previous process is used in the subsequent process. Regarding the operation flow in the claims, the description, and the drawings, even if it is described using “first”, “next”, etc. for convenience, it means that it is essential to carry out in this order. It is not a thing.

DESCRIPTION OF SYMBOLS 100 Movement amount detection apparatus, 110 Camera main body, 112 MCU, 114 motor, 116 Motor drive circuit, 118 Gear train, 119 gear, 120 pinion gear, 122 Two-stage gear, 124 Gear, 130 Encoder, 132 Rotary disk, 134 Optical sensor , 200 lens unit, 202 photographing lens, 204 lens frame, 210 cam ring, 212 cam groove, 214 cam part, 216 drive part, 218 cam follower, 220 acceleration sensor, 222 rack, 224 LPF, 226, 228 resistance, 230, 232 Capacitor, 234 operational amplifier, 236 summing amplifier section, 238, 240, 242 resistance, 244 operational amplifier, 246 capacitor, 248 ADC, 250 DAC

Claims (8)

A pulse signal output unit that outputs a pulse signal as the actuator that moves the moving body is driven;
An acceleration detector for detecting the acceleration of the moving body;
The amount of movement for calculating the amount of movement of the moving body by counting the pulse signal output from the pulse signal output section after the acceleration detecting unit detects the acceleration indicating that the moving body has started moving. A calculation unit;
A moving amount detection device comprising:   The moving amount calculation unit stops counting the pulse signal output from the pulse signal output unit after the acceleration detecting unit detects an acceleration indicating that the moving body has stopped, and The movement amount detection device according to claim 1, wherein the movement amount from the start to the stop is calculated. It is arranged on the upstream side in the drive transmission direction with respect to the moving body, and includes a measuring element that is moved by the actuator,
The movement amount detection device according to claim 1, wherein the pulse signal output unit outputs a movement amount of the probe as a pulse signal.   The movement amount detection device according to claim 3, wherein the measuring element is arranged coaxially with a drive shaft of the actuator. The movement amount detection device according to any one of claims 1 to 4,
Photographic optics,
A cam ring as the moving body for moving the photographing optical system in the optical axis direction;
A lens unit comprising: The movement amount detection device according to any one of claims 1 to 4,
A photographing optical system as the moving body;
A lens unit comprising: The movement amount detection device according to any one of claims 1 to 4,
Photographic optics,
A cam ring as the moving body for moving the photographing optical system in the optical axis direction;
An imaging unit that captures an image formed by the imaging optical system;
An imaging apparatus comprising: The movement amount detection device according to any one of claims 1 to 4,
A photographing optical system as the moving body;
An imaging unit that captures an image formed by the imaging optical system;
An imaging apparatus comprising:

Images