JP5544116B2 - Lens position control device for electronic endoscope - Google Patents

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 mechanism 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. The zoom lens provided at the distal end of the endoscope insertion portion is driven, for example, by transmitting the rotational driving force of a motor provided at the operation portion to the distal end of the insertion portion via a torque wire. The position of the zoom lens is detected using, for example, an encoder provided at the distal end of the insertion portion. However, the configuration in which the sensor is provided at the distal end of the insertion portion is disadvantageous in reducing the diameter of the endoscope insertion portion, and the structure becomes complicated. In order to solve such a problem, a configuration has been proposed in which the lens position is grasped from the time required for the zoom lens to move between the driving ends and the operation time of the zoom switch (Patent Document 1).

Japanese Patent No. 3936512

  However, the configuration as in Patent Document 1 cannot cope with a speed change due to deterioration of a motor or a torque wire over time. It is also possible to grasp the lens position from the rotation angle of the motor, but since the wire is twisted, the rotation range of the motor is wider than the mechanical movable range of the lens, so accurate lens position control is possible. This must be taken into account to do so.

  It is an object of the present invention to reduce the diameter of an insertion portion with a simple and small configuration and to perform lens position control with high accuracy in an electronic endoscope apparatus that drives a lens using a torque wire. It is said.

  The lens position control device for an electronic endoscope according to the present invention includes a lens position adjustment mechanism for adjusting the position of the lens, a motor that supplies power to the lens position adjustment mechanism, and the power of the motor is transmitted to the lens position adjustment mechanism. Detected by the end point detecting means, the end point detecting means for detecting the end point of the movable range of the motor based on the rotational speed of the motor, And an initialization means for detecting the amount of rotation corresponding to the movable range of the motor by driving the motor from one end to the other end of the movable range of the motor, and the rotational amount corresponding to the movable range of the lens and the movable range of the motor And adjusting the position of the lens by controlling the rotation of the motor within the rotation range corresponding to the movable range of the lens.

  The end point detection means monitors the rotation speed based on the number of reference clocks counted while the motor rotates a predetermined amount. The rotation amount detection means generates a pulse signal for every predetermined rotation of the motor, and the end point detection means counts the number of reference clocks in accordance with the timing of the pulse signal and monitors the rotation speed.

  The end point detection means determines that the end point has been reached, for example, when the rotational speed falls below a threshold value. Further, for example, the end point detection means detects a reduction in the rotational speed and determines that the end point has been reached.

  In the initialization means, the correspondence between the lens movable range and the motor rotation amount is specified on the assumption that the center of the lens movable range coincides with the center of the motor movable range. Further, on both sides of the rotation range corresponding to the movable range of the lens for which the rotation of the motor is controlled, for example, a region serving as a margin is provided.

  The motor is preferably a sensorless DC brushless motor or a DC brushless motor for miniaturization, and the rotation of the motor can be detected using a pulse signal generated based on the back electromotive force of one phase. preferable. The amount of rotation is represented by, for example, a count value of the number of pulses of the pulse signal.

  The lens position adjusting mechanism is, for example, a lens position adjusting mechanism for zooming. At the end of the initialization operation, the lens is disposed at the zoom-out (Wide) side end of the movable range of the lens.

  According to the present invention, in an electronic endoscope apparatus that drives a lens using a torque wire, it is possible to reduce the diameter of an insertion portion and perform lens position control with high accuracy with a simple and small configuration. it can.

1 is a schematic diagram illustrating a configuration of an electronic endoscope system according to an embodiment of the present invention. It is a block diagram which shows typically the electrical and mechanical structure of the electronic endoscope (scope main body) 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 rotation of the motor in initialization operation | movement, and the position (lens position) of a cam ring. It is a flowchart of the initialization operation | movement process of this embodiment. It is a graph which shows the change of the motor rotational frequency after a torque wire is twisted and it stops, when rotation of a motor is performed under a substantially constant torque. 4 is a timing chart showing the relationship between a single rotation detection signal FG and a reference clock (pulse) signal CLK output at a constant period. It is a graph for demonstrating the detection method of the end point (detection point) in 1st Embodiment. It is a flowchart of the Tele / Wide end detection process in the first embodiment. It is a graph for demonstrating the detection method of the end point (detection point) in 2nd Embodiment. It is a figure which shows the time-sequential change of the 1 rotation detection signal FG in the deceleration area after abutment to the locking mechanism of a cam ring. It is a flowchart of Tele / Wide end detection processing in the second embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the electronic endoscope system according to the first embodiment of the present invention.

  The electronic endoscope system generally includes a scope main body (electronic endoscope) 10, a processor device 11 to which the scope main body is detachably attached, and a monitor device 12 that displays an endoscopic image. The scope body 11 includes a flexible tube, an insertion portion 13 that is inserted into a body or a tube hole, an operation portion 14 that is gripped / operated by a user and to which a proximal end portion of the insertion portion 13 is coupled, and a processor device 11. And a connector portion 15 that electrically and optically connects the scope main body 10 and the processor device 11 and a universal cord 16 that communicates between the operation portion 14 and the connector portion 15.

  The processor device 11 includes, for example, a light source unit (not shown) together with the image processing unit, and a light guide fiber (not shown) disposed from the light source unit to the distal end of the insertion unit 13 from the connector unit 15. Illumination light is transmitted through and irradiated. The video imaged by the image sensor provided at the distal end of the insertion unit 13 is sent to the processor device 11 via the insertion unit 13, the operation unit 14, the universal cord 16, and the connector unit 15, and predetermined image processing is performed. After being applied, it is displayed on the monitor device 12.

  FIG. 2 is a block diagram schematically showing the electrical configuration of the scope body 10 and the mechanical configuration of the lens driving system shown in FIG.

  An image sensor 17 such as a CCD or CMOS is disposed at the distal end of the insertion portion 13. In the present embodiment, the image pickup device 17 is a CCD, and an image through a lens (lens group) 18 is projected onto the image pickup surface of the CCD 17. The lens 18 includes a zoom lens (lens group) (not shown), and the zoom lens is held by a lens holding frame (not shown) that is slidable in the optical axis direction. As is well known in the art, due to the engagement between the pin provided on the lens holding frame and the cam groove provided on the cam ring 19, the rotational movement around the optical axis of the cam ring 19 is caused in the optical axis direction of the lens holding frame. It is converted into a linear motion, and the position of the zoom lens is adjusted (lens position adjusting mechanism). As a result, the CCD 17 captures an image with a magnification corresponding to the position of a zoom lens (not shown).

  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, and the other end is connected to a motor 22 provided in the operation portion 14 via a reduction gear 23. That is, the rotational force of 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, and a three-phase drive signal (U, V) sent from the motor drive circuit 24 provided in the connector unit 15 via the universal cord 16 (see FIG. 1). , W). The motor drive circuit 24 is controlled by a control unit 25 provided in the connector unit 15, and the motor drive circuit 24 detects the rotation of the motor 22 and outputs it to the control unit 25 as described later.

  The operation unit 14 is provided with an input unit 28 including a tele switch 26 and a wide switch 27 for instructing telephoto (zoom-in / tele) and wide-angle (zoom-out / wide) in the zoom function, respectively. The operation signals of the tele switch 26 and the wide switch 27 are sent to the control unit 25, and the control unit 25 controls the driving including the rotation direction of the motor 22 through the motor drive circuit 24 according to the operation signal.

  The driving of the CCD 17 is controlled by a CCD driving pulse signal output from a CCD driving circuit 29 provided in the connector unit 15, and the CCD driving circuit 29 is controlled by the control unit 25. The image signal generated by the CCD 17 is output to a CCD signal processing unit 30 provided in the connector unit 15. The CCD signal processing unit 30 corresponds to an analog front end, performs first-stage amplification, correlated double sampling, and AD conversion on the analog image signal from the CCD 17 and outputs the result to the control unit 25.

  In addition, a communication control unit 31 is connected to the control unit 25, and the communication control unit 31 receives digital image signals and various control signals input to the control unit 25 as images of the processor device 11 (see FIG. 1). While outputting to a processing unit, the various control signals received from the processor apparatus 11 are input into the control part 25. FIG.

  Next, with reference to FIG. 3 and FIG. 4, the details of the configuration of the motor drive circuit 24 and the control unit 25 in the present embodiment will be described. 3 is a block diagram showing the configuration of the motor drive circuit 24 and the control unit 25, and FIG. 4 shows a three-phase drive signal (U, V, W) output from the motor drive circuit 24 and the motor drive circuit. 24 is a timing chart showing correspondence of one rotation detection signal FG generated at 24. FIG.

In the present embodiment, 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 the startup sequence of the motor 22 and the U, V, and W phase pulse waveforms to be given to the motor 22, and the drive circuit 33 generates the U, The U, V, and W phase voltages that are actually applied to the V and W terminals are output. The U, V, and W signal lines connecting the motor 22 and the three-phase sensorless motor control logic circuit 32 are connected to one input terminal of each of the three comparators 35U, 35V, and 35W, and the other input terminal has a reference voltage. V _REF is input.

  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 this 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 includes a microcomputer 36 and a reference clock counting circuit 37, and the three-phase sensorless motor control logic circuit 32 is controlled by the microcomputer (or FPGA) 36. For example, at least one of back electromotive force detection pulses corresponding to each phase of UVW is input to the microcomputer 36 from the phase detection circuit 34. In the present embodiment, the U phase is used as the single rotation detection signal FG and input to the microcomputer 36. 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, and the lens position is controlled from the motor rotation amount.

  The reference clock counting circuit 37 is supplied with a reference clock signal CLK from a timing generator (not shown) and a one-rotation detection signal FG from the phase detection circuit 34. In the reference clock counting circuit 37, each time the motor 22 rotates once and the rising edge of the FG pulse is detected, the number of clock pulses is counted, and the number of pulses of the reference clock signal CLK during one rotation is sent to the microcomputer 36. (Note that the falling edge of the FG pulse may be used). This count value corresponds to the rotation speed and rotation frequency of the motor 22, and is used in the detection processing of the end points P1 and P2 described later.

  Next, with reference to FIGS. 5 and 6, the lens position initialization operation in the present embodiment will be described. FIG. 5 shows the relationship between the rotation of the motor 22 and the position of the cam ring 19 (lens position) in the initialization operation. The horizontal axis corresponds to the rotation amount of the motor 22 and the vertical axis corresponds to time. FIG. 6 is a flowchart of the initialization operation process of this embodiment. The initialization operation is executed in the microcomputer 36 prior to the lens position control process such as when the electronic endoscope is powered on.

  In the configuration in which the rotational force is transmitted to the lens driving mechanism using the torque wire, even if the movement of the lens (rotation of the cam ring in this embodiment) is stopped by the locking mechanism, the motor is twisted to a constant torque. Rotates until occurs. For this reason, the rotation range (movable range) of the motor is wider than the mechanical movable range of the lens. That is, when the lens position is controlled from the rotation amount of the motor 22, it is necessary to obtain a correspondence between the rotation amount of the motor 22 and the position of the cam ring 19 (lens position) (see FIG. 2).

  In FIG. 5, the left side corresponds to the Tele (telephoto) side, the right side corresponds to the Wide (wide angle) side, and time elapses from top to bottom. In the present embodiment, 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 normal rotation and subtraction during reverse rotation).

  Section A1 shows the movable region (rotatable range) of the motor 22 including displacement due to torsion of the torque wire 21, and section A3 includes the rotation ratio of the motor 22 and the cam ring 19 (including gears 20 and 23). The rotation range of the motor 22 corresponding to the movable range of the cam ring 19 calculated from the gear ratio). For example, when the motor side gear ratio is 1:79, the cam 22 is rotated once for 79 rotations of the motor 22, and when the gear ratio of the torque wire to the cam ring is 1: 3, the cam ring 19 is mechanical. When the rotatable range is 0.5 rotation (180 °), the torque wire requires 1.5 rotations. In the case of the above example, the count number of one rotation detection signal FG over the movable range of the cam ring 19 is 118.5 (= 79 × 1.5).

  Section A <b> 2 indicates an area used for rotation control of the motor 22. That is, it is desirable to provide an extra movable range on the Tele side or Wide side with respect to the mechanical movable range in order to operate the cam ring 19 with a mechanical movable range at the Tele end or Wide end. In this embodiment, the rotatable range of the cam ring 19 calculated from the design value is provided with a margin of 20 pulses on the Tele end side and 30 pulses on the Wide end side.

  In an initial state such as when the endoscope is activated, the positions of the lens 18 and the cam ring 19 are unknown. When the cam ring 19 is at a point P0 in FIG. 5 at the time of activation, in the initialization operation process of the present embodiment, first, in step S100, the rotation of the motor 22 in the Tele direction is started. Next, in step S102, detection processing of the tele end point P1 is started, and the motor 22 is rotated in the tele direction until the tele end point P1 is detected. In step S102, when the tele end point P1 is detected, the rotation of the motor in the tele direction is stopped.

  Next, in step S104, the motor 22 is rotated in the Wide direction, and almost simultaneously, in step S106, counting of one rotation detection signal (pulse signal) FG is started. In step S108, the wide end point P2 detection process is started. The motor 22 is rotated in the Wide direction until the Wide side end point P2 is detected, and when the Wide side end point P2 is detected, the rotation of the motor in the Wide direction is stopped. At this time, the number of FG pulses from point P1 to point P2 is counted.

  The number of pulses between the tele-side end point P1 and the wide-side end point P2 substantially corresponds to the wire movable region A1, and the torsional characteristics of the torque wire 21 are symmetrical with respect to the left and right rotations. The center of A3 coincides with the centers of points P1 and P2. From this, in the initialization operation of the present embodiment, in step S110, the position P3 moved by 90 pulses (60 pulses which is half of the movable range A3 + 30 margins on the wide side) from the center between the end points P1 and P2 to the Wide side. Is the origin in the lens position control process, and the motor 22 is rotated to this position.

  That is, the motor 22 is rotated again from the Wide end point P2 to the Tele side, and the total number of pulses between the end points P1 and P2 is subtracted from the number of pulses in the half section of the cam ring movable range A3 and the number of pulses in the Wide side margin. The rotation of the motor 22 is returned as many times as the number of pulses, and the count value of the FG pulse at this time is stored in the nonvolatile memory or the like as the position information, and the initialization operation process ends.

  Thereafter, with the point P3 as the origin, lens position control is executed in the section A2 based on the operation of the Tele / Wide switches 26 and 27, and the count value of the FG pulse is updated and stored in the memory as position information as needed. . It should be noted that when the count number of the one-rotation detection signal FG over the movable range of the cam ring 19 is 118.5, the Tele end side margin is 20 pulses, and the Wide end side margin is 30 pulses, the area used for control (section) A2) is an interval of 168 pulses (20 + 118 + 30).

  Next, with reference to FIG. 7 and FIG. 8, the principle of endpoint detection in the Tele end point and Wide end point detection processing (Tele / Wide end detection processing) of the present embodiment will be described.

  FIG. 7 shows that when the rotation of the motor 22 in the Tele direction or Wide direction is executed under a substantially constant torque, the rotation of the cam ring 19 is stopped by the locking mechanism after the drive is started, and the torque is It is a graph which shows typically a time change of rotation frequency (rotation speed) of motor 22 until wire 21 is twisted and rotation of motor 22 is stopped substantially. That is, in FIG. 7, the horizontal axis represents time, and the vertical axis represents the rotation frequency of the motor 22.

When the rotation of the motor 22 is started under a substantially constant torque, first, the rotation frequency (rotation speed) rapidly increases (motor rise time T ₀ ), and then becomes a constant frequency, and the rotation is stabilized. Thereafter, when the cam ring 19 hits the locking mechanism and the rotation of the cam ring 19 is stopped, the torque wire 21 begins to be twisted, and the rotational frequency (rotational speed) begins to decrease. When the torque is reached, in principle, the rotation of the motor 22 stops and the rotation frequency (rotation speed) becomes zero.

  However, in actuality, the torque of the motor may decrease between the N pole and S pole of the magnet, and in this application operation, when the rotational torque of the motor 22 reaches the limit of the torque wire twisting torque, This phenomenon occurs, the motor 22 is instantaneously reversed, the wire twist is loosened, and the motor 22 is rotated forward again. For this reason, the rotation of the motor 22 repeats vibration near the end point, and the rotation frequency does not become zero. Therefore, in this embodiment, the end points (points corresponding to P1 and P2 in FIG. 5) are detected by monitoring the gradually decreasing rotational frequency, that is, the rotational speed, not the position where the motor 22 stops (rotational frequency 0). .

  FIG. 8 is a timing chart showing the relationship between the one-rotation detection signal FG and a reference clock (pulse) signal CLK generated inside the control unit. The rotation frequency of the motor 22 is based on the number of pulses (count value) of the reference clock signal that is output during the period (clock pulse counting period) T from the rising edge of one rotation detection signal FG to the next rising edge. It can be calculated. That is, the count value N of the reference clock signal CLK counted by the reference clock counting circuit 37 (see FIG. 3) is proportional to the time required for the motor 22 to make one rotation, and the rotation frequency corresponds to the reciprocal thereof. Therefore, by monitoring the count value N, a change (reduction) in the rotation frequency, that is, the rotation speed can be detected.

  Next, with reference to FIG. 9 and FIG. 10, a method for detecting the Tele side and Wide side end portions (Tele / Wide end detection processing 1) of the first embodiment will be described. FIG. 9 is a graph for explaining an end point (detection point) detection method according to the first embodiment. FIG. 10 is a flowchart of Tele / Wide end detection processing 1. The Tele / Wide end detection process 1 in FIG. 10 corresponds to both the Tele end detection process (Step S102) and the Wide end detection process (Step S108) in FIG.

  As shown in FIG. 9, in the first embodiment, it is assumed that the end points (detection points) P <b> 1 and P <b> 2 are reached when the rotation speed of the motor 22 decreases and reaches a predetermined rotation frequency fc. However, as described above, in the present embodiment, the clock pulse number N counted in the clock pulse counting period (FG pulse pulse interval) T is directly monitored instead of the rotation frequency. The end point detection process is performed based on the above. Since the count value N increases when the rotation frequency (rotation speed) of the motor 22 decreases, in the Tele / Wide end detection processing 1, the end point (P1 or P1) Assume that P2) is detected.

  As shown in FIG. 10, first, in step S200, it is determined whether or not an FG pulse has been detected, and a standby state is maintained from the start of rotation of the motor 22 until the first FG pulse is detected. . When the first FG pulse is detected after the motor 22 is started, the count value N per motor rotation of the reference clock pulse signal CLK is updated in the microcomputer 36 (FIG. 3) in step S202. That is, the number of pulses of the reference clock CLK counted during the clock pulse counting period T is input to the microcomputer 36 from the reference clock counting circuit 37 shown in FIG.

  In step S204, it is determined whether the count value N is larger than a predetermined value. The predetermined value is a rotation speed that is a threshold value, that is, the number of pulses corresponding to the rotation frequency fc in FIG. 9, and the determination in step S <b> 204 corresponds to a determination as to whether or not the rotation speed of the motor 22 has decreased below the threshold value. To do. The threshold value of the rotational speed (or rotational frequency) is set by examining the behavior of the motor 22 in the vicinity of the end in the section where the torque wire is twisted, and based on this, a predetermined value (threshold value) of the count value N is set. Is set. When the count value N is not greater than the predetermined value, the time required for one rotation of the motor 22 is short, and the speed is still too fast to be considered to have reached the end, so the processing is returned to step S202, and the count value N Is updated.

  The processes in steps S202 and 204 are continued until it is determined in step S204 that the count value N is larger than a predetermined value. When N> predetermined value, it is determined that the rotational speed of the motor 22 is lower than the threshold value and has reached the end point P1 or P2. That is, in step S206, the drive of the motor 22 is stopped, and this Tele / Wide end detection process 1 ends.

  As described above, according to the first embodiment of the present invention, while using a sensorless and DC brushless motor, the rotation of the motor is grasped with a simple configuration, and the cam ring or lens is taken into consideration in consideration of the twist of the wire. Since it is possible to take correspondence with the position, it is possible to control the lens position with high accuracy without providing a sensor at the distal end of the insertion portion, to reduce the diameter of the insertion portion, and to reduce the size of the drive portion. Can be planned.

  In the present embodiment, the end point can be detected without overloading the torque wire, and the load on the motor and the torque wire related to the end point detection can be suppressed and the durability can be improved.

  Next, a second embodiment of the present invention will be described with reference to FIGS. The second embodiment is different from the first embodiment only in the method for detecting the tele end point and the wide end point, and the mechanical and electrical configuration is the same as that of the first embodiment, and the description thereof is omitted.

  FIG. 11 corresponds to FIG. 9 in the first embodiment, and is a graph showing a temporal change in the rotational frequency of the motor 22 from the start of driving of the motor 22 until reaching one end point, in the second embodiment. It is a graph for demonstrating the detection method of an end point (detection point). In the first embodiment, the count value of the clock pulse counted per rotation of the motor 22 (corresponding to the time, rotation speed, and rotation frequency per rotation) itself is monitored. In the second embodiment, the count value is monitored. The end point is detected by monitoring the difference value of N. That is, as shown in FIG. 11, the end point is detected by detecting a decrease in the rotational speed of the motor 22.

FIG. 12 shows the time-series change of the one-rotation detection signal FG in the deceleration zone ΔT of FIG. 11 after the cam ring is abutted against the locking mechanism, and the horizontal axis is time t. For example, as shown in FIG. 11, in the deceleration zone ΔT, the rotational speed of the motor 22 is monotonously decelerated, and the FG pulse interval also increases in proportion to the rotational speed. Since the FG pulse interval corresponds to the pulse count value N of the reference clock signal CLK, the latest pulse interval is the latest count value N ₀ , the previous pulse interval is the previous count value N ₋₁ , 2 When the previous pulse interval is represented by the previous count value N- ₂ and the previous pulse interval is represented by the previous count value N- ₃ , during the deceleration, N- ₃ <N- _2. <a _N -1 _{<N 0.} Accordingly, in the second embodiment, the deceleration of the motor 22 is detected by monitoring the value of the _count value difference N− _i− N− _{(i + 1)} , and the end point is detected using this.

  FIG. 13 is a flowchart of Tele / Wide end detection processing 2 employed in the second embodiment. In step S300, as in step S200 (FIG. 10) of the first embodiment, it is determined whether or not the first FG pulse since the start of rotation of the motor 22 has been detected (waveform rising or falling). This process is repeated until the first FG pulse is detected.

Next, in step S302, the values of the four count values N ₀ , N ₋₁ , N ₋₂ , and N _{−3 in} the microcomputer 36 are continuously updated until the condition of step S304 is satisfied, and the condition of step S304 is satisfied. If it is satisfied, the driving of the motor 22 is stopped in step S306, and this process is terminated. That is, in the Tele / Wide end detection process 2 of the second embodiment, the condition of step S304, N ₀ −N ₋₁ > N ₋₁ −N ₋₂ , and N ₋₁ −N ₋₂ > N ₋₂ −N _It is assumed that the end point (P1 or P2) is detected when ₋₃ is satisfied.

In the microcomputer 36, 0 is given as an initial value to the count values N ₀ , N ₋₁ , N ₋₂ , and N ₋₃ , and in the first step S302, the reference clock count circuit 37 is set to the count value N _0. value is entered from (FIG. 3), then the count value _{N 0} is updated, the old values of the count value _{N 0} is shifted to sequentially _{N -1, N -2, N -3} .

  As described above, in the second embodiment, the same effect as that of the first embodiment can be obtained. Further, in the second embodiment, four count values are used in time series, and when the difference between adjacent count values continuously increases twice, the motor rotation speed is decelerated. The end point can be detected at a timing earlier than that of the first embodiment. In addition, erroneous detection due to fluctuations in rotational speed can be prevented, and more accurate end points can be detected.

As an intermediate method between the first embodiment and the second embodiment, two count values N ₀ , N ₋₁ , three count values N ₀ , N ₋₁ , N ₋₂ , or four count values are used. The end point can be detected by detecting the deceleration of the motor from the magnitude of N ₀ , N ₋₁ , N ₋₂ , and N ₋₃ , and the difference between the three count values N ₀ , N ₋₁ , and N ₋₂ can be detected. It is possible to detect the end point by detecting the deceleration of the motor from the comparison, or to combine these and the comparison methods described in the embodiments. It is also possible to detect an end point by setting a threshold value for time differentiation related to the count value N, 1 / N, or the like.

  In this embodiment, the zoom lens is described as an example. However, the present invention is not limited to driving the zoom lens as long as the lens is driven using a torque wire. In this embodiment, the cam ring is used for driving the lens. However, the present invention can be applied to other conventional methods as long as the configuration uses a torque wire.

  In the present embodiment, the rotation of each rotation of the three-phase brushless and sensorless DC motor is detected. However, the n-phase motor may be configured to detect n pulses for each rotation. In this case, the number of pulses of the reference clock counted during 1 / n rotation can be used for detecting the rotation speed (rotation frequency) of the motor. In addition, the count value of the reference clock pulse between two or more single rotation detection signals can be used for detecting the rotation speed (rotation frequency) of the motor. Further, a motor with a sensor can be used. In this case, a sensor detection signal is used.

10 Scope body (electronic endoscope)
DESCRIPTION OF SYMBOLS 11 Processor apparatus 12 Monitor apparatus 13 Insertion part 14 Operation part 15 Connector part 17 Image pick-up element (CCD)
18 Lens 19 Cam ring (Lens position adjustment mechanism)
20 Gear 21 Torque Wire 22 Motor 24 Motor Drive Circuit 25 Control Unit 26 Tele Switch 27 Wide Switch 34 Phase Detection Circuit 36 Microcomputer 37 Reference Clock Counting Circuit

Claims (11)

A lens position adjustment 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;
End point detecting means for detecting an end point of the movable range of the motor based on the rotational speed of the motor;
After detecting one end of the movable range of the motor by the end point detecting means, driving the motor from the one end toward the other end of the movable range of the motor until the other end is detected by the end point detecting means Initializing means for detecting the amount of rotation corresponding to the movable range of the motor by detecting the amount of rotation of the motor
From the amount of rotation corresponding to the movable range of the lens and the amount of rotation corresponding to the movable range of the motor, the rotation of the motor is controlled within the rotational range corresponding to the movable range of the lens to adjust the position of the lens. A lens position control device for an electronic endoscope. 2. The lens position control device for an electronic endoscope according to claim 1 , wherein the end point detection means monitors the rotational speed based on the number of reference clocks counted while the motor rotates a predetermined amount. .   The rotation amount detection means generates a pulse signal for every predetermined rotation of the motor, and the end point detection means counts the number of the reference clocks in accordance with the timing of the pulse signal and monitors the rotation speed. The lens position control device for an electronic endoscope according to claim 2.   4. The lens position control device for an electronic endoscope according to claim 3, wherein the end point detection unit determines that the end point has been reached when the rotational speed is less than a threshold value.   4. The lens position control device for an electronic endoscope according to claim 3, wherein the end point detecting means detects that the end point has been reached by detecting a decrease in the rotational speed.   The initialization means specifies the correspondence between the movable range of the lens and the rotation amount of the motor, assuming that the center of the movable range of the lens coincides with the center of the movable range of the motor. 4. A lens position control device for an electronic endoscope according to 3.   7. The lens position control apparatus for an electronic endoscope according to claim 6, wherein a margin area is provided on both sides of the rotation range corresponding to the movable range of the lens in which the rotation of the motor is controlled. The said motor is a sensorless DC motor, The rotation of the said motor is detected using the pulse signal produced | generated based on the counter electromotive force of one phase, The any one of Claims 1-7 characterized by the above-mentioned. A lens position control device for an electronic endoscope according to Item .   The lens position control device for an electronic endoscope according to claim 8, wherein the rotation amount is represented by a count value of the number of pulses of the pulse signal.   10. The lens position control device for an electronic endoscope according to claim 1, wherein the lens position adjusting mechanism is a zoom lens position adjusting mechanism.   The lens position control device for an electronic endoscope according to claim 10, wherein at the end of the initialization operation, the lens is positioned at an end on the zoom-out side of a movable range of the lens.

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