JP2012075786A - Lens position control system and endoscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the amount of displacement of a lens after the stop of a motor in a constitution which makes the lens move by twisting a torque wire.SOLUTION: An electronic endoscope 10 includes a photographing optical system 18, a cam ring 19, the torque wire 21, the motor 22, a motor driving circuit 24, and a control section 25. The photographing optical system 18 has a zoom optical system displaceable along an optical axis. The zoom optical system is displaced by turning the cam ring 19. The rotation of the motor 22 is transmitted to the cam ring 19 by means of the torque wire 21. The motor driving circuit 24 drives the motor 22. The control section 25 controls the motor driving circuit 24. The duty ratio of a driving voltage applied to the motor 22 is reduced depending on time before the stop. In addition, the change ratio of the duty ratio of the driving voltage to the lapse of the time is set consecutive.

Description

  The present invention relates to an electronic endoscope having a moving mechanism in an optical system, and more particularly to a lens position control device using a torque wire.

  A magnifying endoscope in which an imaging optical system of an electronic endoscope is provided with a zoom mechanism and the observation magnification is variable is known (see Patent Document 1). The zoom lens provided at the distal end of the endoscope insertion tube, for example, by rotating the torque wire in the axial direction by a motor provided at the operation unit, and converting the rotational motion of the torque wire to translational motion at the distal end of the insertion tube, Displacement along the optical axis. It is preferable that the photographing magnification can be adjusted to be a predetermined photographing magnification. For this purpose, it is necessary to stop the displacement of the zoom lens at a predetermined position.

Japanese Patent No. 4249841

  Since it is difficult to use a strong torque wire for an endoscope, the torque wire may be twisted. Therefore, it is difficult to immediately follow the rotation of the torque wire on the motor side to the tip side. Since it is difficult to follow, the zoom lens may be displaced even if the position of the zoom lens or the rotation amount of the motor is detected and the motor is stopped. Therefore, in the configuration as described above, it is difficult to stop the zoom lens from being displaced at a predetermined position.

  A lens position control system according to the present invention includes a lens position adjustment mechanism for adjusting the position of a lens provided at the distal end of an endoscope, a motor for supplying power to the lens position adjustment mechanism, and the power of the motor for adjusting the lens position. A torque wire to be transmitted to the mechanism, a rotation amount detecting means for detecting rotation of the motor and calculating a rotation amount, and a motor control means for performing PWM control so that the motor is rotated by a first rotation amount from a stopped state, The motor control means sets the duty ratio of the drive voltage applied to the motor during the period of rotation from the second rotation amount smaller than the first rotation amount to the first rotation amount as a ratio of the change of the duty ratio over time. It is characterized in that it is decreased as time elapses while substantially continuing.

  The lens is movable from the first end portion to the second end portion, and between the first and second reference positions, which are rotation positions of the motor corresponding to the first and second end portions. 1 to n-th (n is an integer of 2 or more) step positions are defined, and the motor control means performs first, second reference positions, and first to n-th step positions after the start of rotation of the motor. , The rotation of the motor is stopped, and the rotation from the first reference position to the first step position, from the (n−1) th step position to the nth step position, and from the nth step position to the second reference position. The first rotation amount, which is an amount, is between the first reference position and the first step position, between the (n-1) th step position and the nth step position, and between the nth step position and the first step position. 1st rotation drive and nth rotation drive which are rotation drive between 2 reference positions It is preferable to set the end rotary drive each.

  Further, it is preferable that the second rotation amount is determined for each of the first and n-th rotation driving and terminal rotation driving.

  In addition, a switch for switching ON and OFF of the input for moving the lens is provided, and the motor control means rotates the motor until it rotates by the first rotation amount when the switch is turned ON when the motor is stopped. It is preferable that the rotation of the motor is temporarily stopped when the rotation amount is 1, and if the switch is kept on during the temporary stop of the motor, the rotation driving of the motor is started again.

  The endoscope of the present invention supplies power to a lens that is displaceable along the optical axis at the distal end of the insertion tube, a lens position adjustment mechanism for adjusting the position of the lens, and a lens position adjustment mechanism. A motor, a torque wire for transmitting the power of the motor to the lens position adjusting mechanism, a rotation amount detecting means for detecting the rotation of the motor and calculating the rotation amount, and rotating the motor by the first rotation amount from the stopped state. Motor control means for PWM control, and the motor control means sets the duty ratio of the drive voltage applied to the motor during the period of rotation from the second rotation amount smaller than the first rotation amount to the first rotation amount. It is characterized in that the rate of change of the duty ratio with respect to the passage of time is reduced according to the passage of time while being substantially continuous.

  According to the present invention, since the duty ratio of the drive voltage decreases while the duty ratio change rate with respect to time passes continuously before stopping, the torque of the torque wire is gradually released, and the lens after the rotation of the motor 22 stops. It is possible to reduce the amount of displacement.

It is the schematic which shows the structure of the electronic endoscope unit using the endoscope which has the lens position control system which is one Embodiment of this invention. It is a block diagram which shows typically the electrical and mechanical structure of the electronic endoscope of this embodiment. It is a block diagram which shows the structure of a motor drive circuit and a control part. 6 is a timing chart showing a correspondence between a three-phase drive signal (U, V, W) output from the motor drive circuit and a single rotation detection signal generated in the motor drive circuit. It is a figure which shows the relationship between the time change of the duty ratio of the drive voltage applied to a motor, and the time change of the rotation amount of a motor. It is a flowchart of a lens position control process. 4 is a flowchart of a one-step motor rotation control subroutine.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic diagram showing a configuration of an electronic endoscope unit using an endoscope having a lens position control system according to an embodiment of the present invention.

  The electronic endoscope system includes an electronic endoscope 10, an endoscope processor 11, and a monitor 12. The electronic endoscope 10 and the monitor 12 are detachable from the endoscope processor 11.

  The electronic endoscope 10 includes an insertion tube 13, an operation unit 14, a connector 15, and a universal cord 16. The insertion tube 13 is formed by a flexible tube and is inserted into the body or a tube hole.

  The operation unit 14 is gripped and operated by the user, and the proximal end portion of the insertion tube 13 is connected. The connector 15 is attached to and detached from the endoscope processor 11 and electrically and optically connects the electronic endoscope 10 and the endoscope processor 11. The universal cord 16 communicates between the operation unit 14 and the connector 15.

  For example, the endoscope processor 11 includes a light source unit (not shown) together with an image processing unit (not shown). Illumination light is emitted from the light source unit. The illumination light is transmitted to the distal end portion through a light guide fiber (not shown) disposed from the connector portion 15 to the distal end portion of the insertion tube 13, and is irradiated onto a subject near the distal end portion.

  An imaging element (not shown in FIG. 1) is provided at the distal end portion of the insertion tube 13. A subject is photographed by the image sensor. An image signal corresponding to the subject image is generated by photographing with the image sensor.

  The generated image signal is transmitted to the endoscope processor 11 via the insertion tube 13, the operation unit 14, the universal code 16, and the connector unit 15. In the endoscope processor 11, predetermined image processing is performed on the image signal. The image signal is transmitted to the monitor 12, and an image corresponding to the image signal is displayed.

  Next, the configuration of the electronic endoscope 10 will be described with reference to FIG. FIG. 2 is a block diagram schematically showing the configuration of the electronic endoscope 10.

  At the distal end portion of the insertion tube 13, an image sensor 17 and a photographing optical system 18 that are CCDs are arranged. A subject image is formed on the light receiving surface of the image sensor 17 by the photographing optical system 18. The photographing optical system 18 has a zoom optical system (lens group) (not shown) for adjusting the focal length, and the zoom optical system is held by a lens holding frame (not shown) that can slide along the optical axis. The

  As is well known in the art, rotation of the cam ring 19 around the optical axis by engagement of a pin (not shown) provided on the lens holding frame and a cam groove (not shown) provided on the cam ring 19. The movement is converted into a linear movement in the optical axis direction of the lens holding frame, and the position of the zoom optical system is adjusted (lens position adjusting mechanism). Thereby, the image sensor 17 captures an image with a magnification according to the position of the zoom optical system.

  A gear portion (not shown) is formed on the outer peripheral surface of the cam ring 19 along the circumferential direction, and the gear 20 is engaged with the gear portion. One end of a torque wire 21 disposed in the insertion portion 11 is connected to the gear 20.

  The other end of the torque wire 21 is connected to a motor 22 provided in the operation unit 14 via a reduction gear 23. Therefore, the rotational force generated by rotating the motor 22 is transmitted to the gear 20 via the torque wire 21, and the cam ring 19 is rotated around the optical axis.

  The motor 22 is, for example, a three-phase sensorless / brushless / DC motor. The motor 22 is controlled by a three-phase drive signal (U, V, W) sent from the motor drive circuit 24 provided in the connector unit 15 via the universal cord 16 (see FIG. 1).

  The motor drive circuit 24 outputs a three-phase drive signal based on control by the control unit 25 provided in the connector unit 15. The rotation of the motor 22 is detected by the motor drive circuit 24 and transmitted to the control unit 25.

  The operation unit 14 is provided with an input unit 28 including a Tele button 26 and a Wide button 27. By pressing the Tele button 26, an instruction to execute telephoto (zoom-in) can be input. An instruction to execute wide angle (zoom out) can be input by pressing the Wide button 27.

  Operation signals for the Tele button 26 and the Wide button 27 are sent to the control unit 25. The control unit 25 controls the motor drive circuit 24 based on this operation signal, and rotates the motor 22.

  The image sensor 17 is controlled by a CCD drive pulse signal output from a CCD drive circuit 29 provided in the connector unit 15. The CCD drive circuit 29 is controlled by the control unit 25. The image signal generated by the image sensor 17 is transmitted to the CCD signal processing unit 30 provided in the connector unit 15.

  The CCD signal processing unit 30 is an analog front end, and performs first-stage amplification, correlated double sampling, and AD conversion on the analog image signal generated by the image sensor 17 and outputs the result to the control unit 25.

  In addition, a communication control unit 31 is connected to the control unit 25. The communication control unit 31 outputs digital image signals and various control signals input to the control unit 25 to the image processing unit of the endoscope processor 11 and also controls various control signals received from the endoscope processor 11. 25.

  Next, with reference to FIG. 3, FIG. 4, the detail of the structure of the motor drive circuit 24 and the control part 25 in this embodiment is demonstrated. FIG. 3 is a block diagram showing the configuration of the motor drive circuit 24 and the control unit 25. FIG. 4 is a timing chart showing the correspondence between the three-phase drive signals (U, V, W) output from the motor drive circuit 24 and the one-rotation detection signal generated in the motor drive circuit 24.

  The motor drive circuit 24 includes a three-phase sensorless motor control logic circuit 32, a drive circuit 33, a phase detection circuit 34, and the like. The three-phase sensorless motor control logic circuit 32 generates U, V, and W phase pulse waveforms to be given to the motor 22. The drive circuit 33 outputs U, V, and W phase voltages applied to the U, V, and W terminals of the motor 22 based on the U, V, and W phase pulse waveforms.

U, V, and W signal lines connecting the motor 22 and the drive circuit 33 are connected to one input terminals of the comparators 35U, 35V, and 35W, respectively. Further, the reference voltage _VREF is input to the other input terminals of the comparators 35U, 35V, and 35W.

  When the voltage applied to each phase of the UVW is in an off state, a negative voltage is generated by the counter electromotive force in the corresponding phase. In the present embodiment, each of the comparators 35U, 35V, and 35W detects the occurrence of the counter electromotive force of each phase, and the phase detection circuit 34 detects the phase of the motor 22.

  In addition, since the output from the comparator for one phase is a pulse signal having a period corresponding to one rotation of the motor 22, this is output to the control unit 25 as a one-rotation detection signal FG in this embodiment. FIG. 4 also shows the timing of phase detection in each phase.

  The control unit 25 is provided with a microcomputer 36 and a nonvolatile memory 37. The three-phase sensorless motor control logic circuit 32 is controlled by the microcomputer 36. A reverse power detection pulse corresponding to the U phase is input from the phase detection circuit 34 to the microcomputer 36 as a single rotation detection signal.

  In the microcomputer 36, a rotation amount corresponding to the rotation angle of the motor 22 is calculated based on the one-rotation detection signal FG. The rotation amount of the motor 22 is obtained as a count value of the one-rotation detection signal FG (for example, the number of pulses obtained by addition during forward rotation and subtraction during reverse rotation). In the electronic endoscope 10, the lens position is controlled based on the motor rotation amount.

  The rotation position of the motor that positions the zoom optical system at the Tele end is determined as the first reference position. The current position of the zoom optical system is estimated based on the amount of rotation from the first reference position calculated when the motor 22 is rotated. The calculated rotation amount is also stored in the nonvolatile memory 37.

  The rotation amount from the origin position when the zoom optical system is positioned at the Wide end is calculated in advance as the second reference position and stored in the nonvolatile memory 37. In addition, the first to eighth step rotation positions are determined in advance between the first reference position and the second reference position, and are stored in the nonvolatile memory 37.

  The motor drive circuit 24 drives the motor 22 so that the zoom optical system is positioned at any of the Tele end, the position of the zoom optical system corresponding to the first to eighth step rotation positions, and the Wide end.

  That is, when the Tele button 26 is pressed at the first reference position and the first to eighth step rotation positions, the motor 22 rotates until the first to eighth step rotation positions and the second reference position are reached. Driven by.

  Further, when the pressed state of the Tele button 26 is maintained, the rotation of the motor 22 is temporarily stopped at each step rotation position, and the rotation is resumed after the interval time set by the user has elapsed. The interval time can be set by the user from 10, 41, 60 msec, for example.

  In addition, after the Tele button 26 is released, the motor 22 is driven to rotate to a position that reaches the first of the first to eighth step rotation positions or the second reference position.

  Similarly, when the Wide button 27 is pressed at the second reference position and the eighth to first step rotation positions, the motor 22 rotates until the eighth to first step rotation positions and the first reference position are reached. To be driven.

  If the pressed state of the Wide button 27 is maintained, the rotation of the motor 22 is temporarily stopped at each step rotation position, and the rotation is resumed after the interval time set by the user has elapsed. In addition, after the wide button 27 is released, the motor 22 is driven so as to rotate to the first position reached in the eighth to first step rotation positions or the first reference position.

  Next, driving of the motor 22 will be described with reference to the timing chart of FIG. FIG. 5 is a graph showing the relationship between the change over time in the duty ratio of the drive voltage applied to the motor 22 and the change over time in the amount of rotation of the motor 22.

  The torque of the motor 22 is adjusted by PWM control. That is, the torque is adjusted by changing the duty ratio of the drive voltage of the motor 22.

  Before pressing the Tele button 26 and the Wide button 27, the duty ratio of the drive voltage is maintained at zero, and the motor 22 is in any of the first, second reference positions, or the first to eighth step rotation positions. The rotation is stopped at.

  When the Wide button 27 is pressed at any of the first reference position and the first to eighth step rotation positions, the duty ratio of the drive voltage is switched to the lowest drive value. During the period from the original position to the adjacent step rotation position or the second reference position, the duty ratio D of the drive voltage is controlled so as to satisfy the expression (1).

In the equation (1), D _min is the minimum driving value, D _A is a constant, and is determined to be an optimum value through experiments or the like. In addition, the time constant T in the equation (1) is a constant determined so as to satisfy the equation (2), and is between the first reference position and the first step rotation position, the nth and (n + 1) th. ) Step rotation positions (n is an integer of 1 to 7) and between the eighth step rotation position and the second reference position, and are stored in the nonvolatile memory 37.

  In the equation (2), ΔFG is a rotation amount between the reference position and the step rotation position adjacent to each other or the step rotation positions adjacent to each other like the first reference position and the first step rotation position (first rotation amount). It is.

  When the Wide button is pressed when the rotation position of the motor 22 is the first reference position, a time constant T determined between the first reference position and the first step rotation position is read to the microcomputer 36. The duty ratio of the drive voltage is controlled so as to satisfy the equation (1).

  The rotation position of the motor 22 is determined relative to the nth and (n + 1) th step rotation positions when the Wide button is pressed at the nth step rotation position (n is an integer of 1 to 7). The time constant T is read by the microcomputer 36 and controlled so that the duty ratio of the drive voltage satisfies the equation (1).

  When the Wide button is pressed when the rotation position of the motor 22 is the eighth step position, the microcomputer 36 reads a time constant T determined between the eighth step rotation position and the second reference position. The duty ratio of the drive voltage is controlled so as to satisfy the equation (1).

  When the motor 22 reaches the adjacent step rotation position or the second reference position from the original position, the duty ratio of the drive voltage is switched to zero.

  When the depression of the Wide button 27 is released while the motor 22 is rotating, the duty ratio of the drive voltage is maintained at zero. When the Wide button 27 is pressed even after the rotation of the motor 22 is stopped, the duty ratio of the drive voltage is switched to the minimum drive value when the set interval time has elapsed since the motor 22 stopped rotating. Similarly, the duty ratio of the drive voltage is adjusted.

  When the Tele button 26 is depressed at any of the second reference position and the eighth to first step rotation positions, the duty ratio of the drive voltage is switched to the lowest drive value. In addition, when the Wide button 27 is pressed, the normal phase and the reverse phase of the drive voltage are switched.

  During the period from the original position to the adjacent step rotation position or the first reference position, the duty ratio D of the drive voltage is controlled so as to satisfy the expression (1).

  Note that when the Tele button is pressed when the rotation position of the motor 22 is the second reference position, a time constant T determined between the eighth step rotation position and the second reference position is given to the microcomputer 36. It is read out and controlled so that the duty ratio of the drive voltage satisfies the equation (1).

  When the Tele button is pressed when the rotational position of the motor 22 is the nth step rotational position (n is an integer of 2 to 8), the (n-1) th relative to the nth step rotational position. A predetermined time constant T is read out to the microcomputer 36, and the duty ratio of the drive voltage is controlled so as to satisfy the expression (1).

  When the Tele button is pressed when the rotation position of the motor 22 is the first step rotation position, the time constant T defined between the first reference position and the first step rotation position is a microcomputer 36. And the duty ratio of the drive voltage is controlled so as to satisfy the equation (1).

  When the motor 22 reaches the adjacent step rotation position or first reference position from the original position, the duty ratio of the drive voltage is switched to zero.

  When the pressing of the Tele button 26 is released while the motor 22 is rotating, the duty ratio of the drive voltage is maintained at zero. When the Tele button 26 is pressed after the rotation of the motor 22 is stopped, the duty ratio of the drive voltage is switched to the minimum drive value when the set interval time has elapsed since the rotation of the motor 22 is stopped. Similarly, the duty ratio of the drive voltage is adjusted.

  Next, lens position control processing executed by the microcomputer 36 after the initialization operation will be described with reference to the flowchart of FIG. FIG. 6 is a flowchart of the lens position control process, which is executed by the microcomputer 36 when either the Tele button 26 or the Wide button 27 is pressed.

  In step S100, it is determined which of the Tele button 26 and the Wide button 27 has been pressed. If the Tele button 26 has been pressed, the process proceeds to step S101. If the Wide button 27 has been pressed, the process proceeds to step S103.

  In step S101, it is determined whether or not the rotational position of the motor 22 is the first reference position. If it is the first reference position, it cannot be rotated in the Tele direction, and the process returns to step S100. If the position is other than the first reference position, the process proceeds to step S102.

  In step S102, the rotation direction of the motor 22 is set to the Tele direction. After setting the rotation direction, the process proceeds to step S200.

  On the other hand, in step S103, it is determined whether or not the rotational position of the motor 22 is the second reference position. If it is the second reference position, since it cannot be rotated in the Wide direction, the process returns to step S100. If the position is other than the second reference position, the process proceeds to step S104.

  In step S104, the rotation direction of the motor 22 is set to the Wide direction. After setting the rotation direction, the process proceeds to step S200.

  In step S200 after step S102 or step S104, the motor 22 is driven to rotate from the current rotational position of the motor 22 to an adjacent rotational position in the set rotational direction. After the rotation control of the motor 22, the process proceeds to step S105.

  In step S105, the rotation of the motor 22 is stopped. After the motor 22 is stopped, the process proceeds to step S106. In step S106, an interval timer is activated. After starting the interval timer, the process proceeds to step S107.

  In step S107, it is determined whether or not the set interval time has elapsed. If the set interval time has not elapsed, the process returns to step S107, and step S107 is repeated until the interval time elapses. When the interval time has elapsed, the process returns to step S100.

  Next, the one-stage motor 22 rotation control executed in step S200 will be described with reference to the flowchart of FIG. FIG. 7 is a subroutine of one-stage motor 22 rotation control.

  In step S201, the corresponding time constant T is read from the nonvolatile memory 37 based on the current rotational position of the motor 22 and the rotational direction set in step S102 or step S104. After reading the time constant T, the process proceeds to step S202.

  In step S202, using the time constant T read in step S201, a function of the duty ratio of the drive voltage with respect to time is determined. After setting the duty ratio, the process proceeds to step S203.

  In step S203, the duty ratio of the drive voltage applied to the motor 22 is set to the minimum drive value, and the rotation of the motor 22 is started. After the motor 22 starts rotating, the process proceeds to step S204.

  In step S204, adjustment of the duty ratio is started so as to vary depending on the function set in step S202 over time. After the duty ratio adjustment is started, the process proceeds to step S205.

  In step S205, it is determined whether or not the rotational position of the motor 22 has reached the reference position or step rotational position adjacent to the original position in the set rotational direction. If not, the process returns to step S205, and step S205 is repeated until the adjacent rotational position is reached. If it has reached the adjacent rotational position, the process proceeds to step S105.

  As described above, according to the lens position control system of the present embodiment, the torque can be gradually released by reducing the duty ratio of the drive voltage from the normal drive voltage before stopping the rotation of the motor 22. . By gradually releasing the torque, it is possible to reduce the amount of displacement of the zoom optical system after the motor 22 stops rotating.

  Further, according to the present embodiment, the duty ratio is changed in a sinusoidal function with the passage of time. Therefore, when the duty ratio is decreased from the minimum value to the minimum drive value, it is possible to make the ratio of the change of the duty ratio with the passage of time continuous.

  By continuing the rate of change of the duty ratio over time, the torque can be released more slowly than when changing at a constant rate. Accordingly, it is possible to further reduce the amount of displacement of the zoom optical system after the rotation of the motor 22 is stopped.

  Since the amount of displacement of the zoom optical system after stopping the rotation of the motor 22 can be reduced, the displacement of the zoom optical system can be stopped at a position closer to a predetermined position. Therefore, since accurate position adjustment is possible, there is no need to provide a position detection sensor of the zoom optical system at the distal end of the insertion tube 13.

  In the present embodiment, the duty ratio of the drive voltage is changed in a sine function with respect to time, but the change of the duty ratio with respect to time is not limited to the sine function. While the rotation ratio between the original rotation position and the adjacent rotation position (second rotation amount) until the rotation is stopped, the duty ratio changes substantially continuously with the passage of time while maintaining the duty ratio. If it is the structure which reduces a ratio, it is possible to acquire the effect similar to this embodiment.

In this embodiment, the motor 22 is started to rotate and the duty ratio of the drive voltage is controlled to gradually increase. However, the motor 22 may be boosted to a constant value at the start of rotation. That boosts the D _{min +} D _A at the start rotating, to obtain the same effect as also present embodiment by adjusting the duty ratio so as to change according to the post-rotation after the start T / 2 has elapsed (1) Is possible.

  In the present embodiment, the rotation of the motor 22 is stopped at the first to eighth step rotation positions, but is not limited to the first to eighth step rotation positions. The configuration may be such that the rotation of the motor 22 is stopped at the first to nth step rotation positions (n is an integer of 2 or more).

  By stopping the rotation of the motor 22 at the first to nth step rotation positions between the first and second reference positions, the subject can be observed at a predetermined photographing magnification. In addition, with the configuration in which the rotation of the motor 22 is stopped at each step rotation position for the set interval time, the displacement of the zoom optical system can be stopped at a magnification desired by the user.

  Moreover, in this embodiment, although it is the structure which stops rotation of the motor 22 in the 1st-8th step rotation position, it is not necessary to stop in any position. In other words, the configuration may be such that the rotation of the motor 22 is stopped only at the first and second reference positions. Even in a configuration in which the rotation of the motor 22 is stopped only at the first and second reference positions, it is possible to obtain an effect of reducing the amount of displacement of the zoom optical system after the rotation is stopped.

  In the present embodiment, the rotation amount of the motor 22 is detected from the phase of the three-phase drive signal output from the motor control circuit 24. However, the rotation amount of the motor 22 can be detected by any other method. Good. For example, the configuration may be such that the rotation amount is detected by a position detection sensor such as an encoder that detects the rotation position of the motor 22.

  In this embodiment, the zoom optical system is displaced. However, what is driven by the torque wire is not limited to the zoom optical system. A configuration in which another lens such as a focus lens is driven may be employed.

  In this embodiment, the cam ring is used for driving the lens. However, any other known mechanism can be applied as long as the driving force is transmitted by rotating the torque wire. is there.

DESCRIPTION OF SYMBOLS 10 Electronic endoscope 11 Endoscope processor 12 Monitor 13 Insertion tube 14 Operation part 17 Image pick-up element 18 Shooting optical system 19 Cam ring (lens position adjustment mechanism)
20 Gear 21 Torque wire 22 Motor 24 Motor drive circuit 25 Control unit 26 Tele button 27 Wide button 34 Phase detection circuit 36 Microcomputer 37 Non-volatile memory

Claims (5)

A lens position adjustment mechanism for adjusting the position of the lens provided at the distal end of the endoscope;
A motor for supplying power to the lens position adjusting mechanism;
A torque wire that transmits the power of the motor to the lens position adjusting mechanism;
A rotation amount detecting means for detecting rotation of the motor and calculating a rotation amount;
Motor control means for performing PWM control so that the motor is rotated by a first rotation amount from a stopped state;
The motor control means sets a duty ratio of a drive voltage applied to the motor to a time passage during a period of rotation from the second rotation amount smaller than the first rotation amount to the first rotation amount. The lens position control system, wherein the ratio of the change in the duty ratio with respect to is decreased with the passage of time while being substantially continuous. The lens is movable from a first end to a second end;
First to nth (n is an integer of 2 or more) step positions are defined between the first and second reference positions, which are rotation positions of the motor corresponding to the first and second end portions. And
The motor control means stops the rotation of the motor at the first and second reference positions and the first to n-th step positions after starting the rotational drive of the motor,
Rotation amount from the first reference position to the first step position, from the (n−1) th step position to the nth step position, and from the nth step position to the second reference position The first rotation amount is between the first reference position and the first step position, between the (n-1) th step position and the nth step position, and It is defined for every 1st rotation drive which is rotation drive between the nth step position and the 2nd standard position, nth rotation drive, and final rotation drive. Lens position control system.   3. The lens position control system according to claim 2, wherein the second rotation amount is determined for each of the first, n-th rotation drives, and the terminal rotation drive. 4. A switch for switching ON and OFF of an input for moving the lens;
The motor control means includes
When the switch is turned ON while the motor is stopped, the motor is rotated until it rotates by the first rotation amount,
When the motor rotates by the first rotation amount, the rotation of the motor is temporarily stopped,
The rotation drive of the motor is started again when the ON state of the switch is continued during the temporary stop of the motor. Lens position control system. A lens provided so as to be displaceable along the optical axis at the tip of the insertion tube;
A lens position adjusting mechanism for adjusting the position of the lens;
A motor for supplying power to the lens position adjusting mechanism;
A torque wire that transmits the power of the motor to the lens position adjusting mechanism;
A rotation amount detecting means for detecting rotation of the motor and calculating a rotation amount;
Motor control means for performing PWM control so that the motor is rotated by a first rotation amount from a stopped state;
The motor control means sets a duty ratio of a drive voltage applied to the motor to a time passage during a period of rotation from the second rotation amount smaller than the first rotation amount to the first rotation amount. The endoscope is characterized in that the ratio of the change of the duty ratio with respect to is decreased with the passage of time while being substantially continuous.

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