Lens position control device and endoscope apparatus

Abstract

To provide a lens position control device and an endoscope apparatus that enable simpler and more accurate lens position control than before.SOLUTION: There is provided a lens position control device for controlling a position of a variable power lens of a zoom optical system provided in an endoscope, the lens position control device comprising a brush-added DC motor for generating driving force for changing the position of the variable power lens, a drive circuit for driving the brush-added DC motor by repeating an application state in which drive voltage is applied between a pair of terminals of the brush-added DC motor and an open state in which a portion between the terminals is opened, and a processor for controlling the position of the variable power lens on the basis of a time integral value of counter electromotive force generated at the brush-added DC motor in the open state.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The technology of the present disclosure relates to a lens position control device and an endoscope device. [Background technology]

[0002] There is known an endoscope that has an insertion section that is inserted into the body of a subject and captures an image of an observation site inside the body using an imaging unit disposed at the tip of the insertion section. The imaging unit has an imaging element and an optical system that forms an image of the observation site on the imaging element. The optical system of the endoscope may be a zoom optical system that has a zoom function. In this case, the endoscope is provided with a zoom mechanism that moves a variable magnification lens of the zoom optical system.

[0003] The variable magnification lens is a movable lens that moves in the optical axis direction, and changes the shooting magnification of the zoom optical system by moving in the optical axis direction. The zoom mechanism includes a motor that generates a driving force for driving the variable magnification lens, and a driving force transmission mechanism that transmits the driving force of the motor to the variable magnification lens through a wire or the like. When the focal length of the optical system is switched stepwise to a plurality of pre-set focal lengths, as in so-called step zoom, it is necessary to move the variable magnification lens to a target position corresponding to the plurality of focal lengths, so the zoom mechanism is provided with a lens position control device that controls the position of the variable magnification lens through control of the motor (see, for example, Patent Documents 1 and 2).

[0004] The position of the variable magnification lens is controlled through the rotation control of the motor, and there are various control methods. For example, there is a method in which the rotation of the motor is detected through a sensor such as an encoder, and the amount of rotation of the motor is detected by feeding back the detection signal. However, feedback control requires a signal line to receive the detection signal from the sensor, and is not preferable for endoscopes in which it is desirable to reduce the number of wires in the thin-diameter tubular portion as much as possible. There is also a method of using a stepping motor that can accurately control the amount of rotation by counting the number of input drive pulses, but stepping motors are disadvantageous in terms of cost and size when used in endoscopes compared to DC motors.

[0005] Therefore, the lens position control devices described in Patent Document 1 and Patent Document 2 use a sensorless DC (Direct Current) motor that does not use a sensor for feedback control, and control the position of the variable magnification lens by controlling the rotation of the DC motor. The lens position control device described in Patent Document 1 uses a brushless DC motor driven by a three-phase drive pulse. Then, a one-rotation detection signal indicating that the DC motor has rotated once is obtained by detecting the generation timing of the back electromotive force generated in the brushless DC motor. The lens position control device described in Patent Document 1 detects the amount of rotation of the DC motor based on the one-rotation detection signal, and controls the position of the variable magnification lens. Moreover, the lens position control device described in Patent Document 2 controls the amount of rotation of the DC motor by counting the drive time for driving the DC motor, and controls the position of the variable magnification lens. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 5219931 [Patent Document 2] Patent No. 6140362 Summary of the Invention [Problem to be solved by the invention]

[0007] However, the lens position control device described in Patent Document 1 uses a three-phase brushless DC motor, which causes a problem that the configuration of the motor and the drive circuit is more complicated than when a DC motor with a brush is used. Also, the lens position control device described in Patent Document 2 controls the rotation amount of the DC motor by counting the drive time for driving the DC motor, so there is a risk that the accuracy of the position control of the variable magnification lens will decrease if the rotation speed of the DC motor fluctuates due to load fluctuations.

[0008] The technique disclosed herein provides a lens position control device and an endoscope device that are simpler in configuration and capable of controlling a lens position with higher accuracy than conventional devices. [Means for solving the problem]

[0009] In order to achieve the above-mentioned object, the lens position control device according to the technique disclosed herein is a lens position control device that controls the position of a variable magnification lens of a zoom optical system provided in an endoscope, and includes a brushed DC motor that generates a driving force for changing the position of the variable magnification lens, a driving circuit that drives the brushed DC motor by repeating an applied state in which a driving voltage is applied between a pair of terminals of the brushed DC motor and an open state in which the terminals are opened, and a processor that controls the position of the variable magnification lens based on the time integral value of the back electromotive force generated in the brushed DC motor in the open state.

[0010] It is preferable that the processor obtains an average voltage by averaging the drive voltage and the back electromotive force, and obtains a time integral value of the back electromotive force based on the average voltage and a known drive pulse corresponding to the drive voltage.

[0011] It is preferable to provide a low-pass filter that outputs to a processor an average voltage output signal obtained by smoothing input signals corresponding to the waveforms of the drive voltage and back electromotive force generated between the terminals.

[0012] It is preferable that the processor performs step zoom control for gradually changing the position of the magnification variable lens to a plurality of preset target positions, thereby gradually changing the focal length of the zoom optical system.

[0013] It is preferable that a correspondence between a plurality of target positions of the variable lens and the time integral value of the back electromotive force required to move the variable lens to each target position is stored in advance in a memory, and the processor controls the position of the variable lens based on the correspondence obtained from the memory.

[0014] It is preferable that the driving force transmission mechanism includes a torque wire that transmits the driving force of the brushed DC motor to the variable magnification lens, and a reducer that reduces the rotation of the brushed DC motor and transmits it to the torque wire, the reducer having an output shaft connected to the torque wire and rotating the torque wire around its axis.

[0015] It is preferable that the variable magnification lens moves from the wide-angle end to the telephoto end within a range of one rotation of the output shaft.

[0016] When the rotational position of the output shaft when the variable magnification lens is at one of the wide end or telephoto end is defined as a first end point position, and when the rotational position of the output shaft when the variable magnification lens is at the other end is defined as a second end point position, the variable magnification lens is provided with an abutment portion that abuts against the output shaft at each of the first end point position and the second end point position, thereby regulating the rotation of the output shaft, and it is preferable that the processor monitors the back electromotive force while driving the brushed DC motor, and detects that the variable magnification lens has reached the wide end or telephoto end when the back electromotive force reaches a value corresponding to a state in which the brushed DC motor has stopped rotating.

[0017] It is preferable that the drive circuit drives the brushed DC motor by repeating three states: an applied state, an open state, and a short-circuit state in which the terminals are short-circuited.

[0018] Preferably, the processor monitors the back EMF while driving the brushed DC motor and utilizes the back EMF for control.

[0019] It is preferable that the processor controls the rotation speed of the brushed DC motor by adjusting the ratio of the time during which the drive voltage is applied through the drive circuit based on the result of comparing the back electromotive force with a preset reference value.

[0020] It is preferable that the processor detects abnormalities including at least one of an abnormality in the brushed DC motor and a break in wiring between the drive circuit and the brushed DC motor based on the back electromotive force.

[0021] The endoscopic device related to the technology disclosed herein is an endoscopic device including an endoscope provided with a zoom optical system and a lens position control device that controls the position of a variable lens of the zoom optical system, and the lens position control device includes a brushed DC motor that generates a driving force for changing the position of the variable lens, a driving circuit that drives the brushed DC motor by repeating an applied state in which a driving voltage is applied between a pair of terminals of the brushed DC motor and an open state in which the terminals are opened, and a processor that controls the position of the variable lens based on the time integral value of the back electromotive force generated in the brushed DC motor in the open state. Effect of the Invention

[0022] According to the technology of the present disclosure, it is possible to control the lens position with a simpler configuration and with higher accuracy than in the past. [Brief description of the drawings]

[0023] [Figure 1] 1 is a diagram showing an overall configuration of an endoscope system. [Diagram 2] FIG. 2 is a diagram showing a main part of a zoom mechanism. [Diagram 3] FIG. 2 is a diagram illustrating a configuration of a motor control unit. [Figure 4] 1 is a time chart of the terminal voltage of a DC motor. [Diagram 5] 1 is a graph showing the relationship between the rotation speed and the back electromotive force of a DC motor. [Figure 6] FIG. 2 is a diagram illustrating the processing of a processor. [Figure 7] FIG. 4 is a diagram showing lens target position information. [Figure 8] 10 is a flowchart showing a procedure for lens position control. [Figure 9] FIG. 11 is a diagram showing an effect of the first embodiment. [Figure 10] 13 is a flowchart showing a procedure for detecting an end point. [Figure 11] 13 is a time chart of the terminal voltage of a DC motor in the second embodiment. [Figure 12] FIG. 13 is a diagram showing the time ratio of a short-circuited section. [Figure 13] FIG. 13 is a diagram illustrating a configuration of a motor control unit according to a third embodiment. [Figure 14] FIG. 11 is a diagram illustrating an example of a process for detecting a back electromotive force. [Figure 15] FIG. 11 is a diagram illustrating another example of a process for detecting a back electromotive force. [Figure 16] 10 is a flowchart showing a procedure for speed control based on a back electromotive force. [Figure 17] 10 is a flowchart showing a procedure for detecting an abnormality based on a back electromotive force. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] "First embodiment" [Overall configuration of endoscope system] Fig. 1 is a schematic diagram showing an overall configuration of an endoscope system 9 to which a lens position control device and an endoscope device according to the technology of the present disclosure are applied. As shown in Fig. 1, the endoscope system 9 includes an endoscope 10, a light source device 11, a processor device 12, and a monitor 13. The endoscope system 9 is used for endoscopic examination of the inside of a subject such as a patient. The endoscope 10 is an endoscope inserted into a digestive tract such as the large intestine and the esophagus, and is a flexible soft endoscope. The endoscope 10 includes an insertion section 17 inserted into the digestive tract, an operation section 18 connected to the base end side of the insertion section 17 and held by an operator to perform various operations, and a universal cord 19 connected to the operation section 18.

[0025] The light source device 11 supplies the endoscope 10 with illumination light that illuminates an observation site inside the body. The processor device 12 processes an image captured by the endoscope 10 to generate an observation image 16. The observation image 16 is displayed on a monitor 13. A doctor, who is a user, proceeds with the endoscopic examination while checking the observation image 16. The observation image 16 displayed on the monitor 13 is basically a moving image, but it is also possible to display a still image as the observation image 16 as necessary.

[0026] The insertion section 17 is a thin-diameter, long tubular section, and is configured by connecting a flexible section 21, a bending section 22, and a distal section 23 in this order from the base end side to the distal end side. The flexible section 21 is flexible. The bending section 22 is a section that can be bent by operating the operation section 18. The distal section 23 is provided with an imaging unit 41 and the like. Although not shown, the distal surface of the distal section 23 is provided with an illumination window that illuminates the observation site with illumination light, an observation window into which subject light reflected from the illumination light by a subject enters, a treatment tool outlet for allowing a treatment tool to protrude, and a cleaning nozzle for cleaning the observation window by injecting gas and water into the observation window.

[0027] A light guide (not shown), a signal cable, an operating wire (not shown), a conduit (not shown) for inserting a treatment tool, and the like are provided within the insertion portion 17. The light guide extends from the universal cord 19 and guides illumination light supplied from the light source device 11 to an illumination window in the tip portion 23. The signal cable is used for communication of image signals from the imaging unit 41 and control signals for controlling the imaging unit 41, as well as for supplying power to the imaging unit 41. Like the light guide, the signal cable also extends from the universal cord 19 and is disposed to the tip portion 23.

[0028] The operation wire is a wire for operating the bending portion 22, and is disposed between the operation portion 18 and the bending portion 22. The treatment tool insertion conduit is a conduit for inserting a treatment tool (not shown) such as forceps, and is disposed from the operation portion 18 to the tip portion 23. In addition, a fluid tube for supplying air and water is provided inside the insertion portion 17. The fluid tube supplies gas and water to the tip portion 23 for cleaning the observation window.

[0029] In addition, a torque wire 42 is disposed within the insertion section 17. The imaging unit 41 has a zoom function capable of changing the imaging magnification. As described later, the torque wire 42 is used to change the imaging magnification of the imaging unit 41. The torque wire 42 is flexible and can rotate around its axis. The torque wire 42 extends from the distal end 23 where the imaging unit 41 is provided to the operation section 18 on the proximal end side.

[0030] The operation unit 18 is provided with a DC motor 43 that rotates the torque wire 42 and a reducer 44 that reduces the rotation of the DC motor 43. One end of the base end side of the torque wire 42 is connected to an output shaft 45 of the reducer 44. The DC motor 43 is a brushed DC motor. The DC motor 43 generates a driving force for changing the position of the variable magnification lens 51B (see FIG. 2) in the imaging unit 41 as described later. As is well known, a brushed DC motor is a motor having brushes that contact a commutator connected to a coil wound around a rotor. The brushed DC motor has a simpler configuration than a brushless DC motor, and the configuration of the drive circuit is also simple. The DC motor 43 is an example of a "brushed DC motor" according to the technology of the present disclosure.

[0031] In addition, the operation unit 18 is provided with various operation members operated by the surgeon. Specifically, the operation unit 18 is provided with two types of bending operation knobs 27, an air / water supply button 28, a suction button 29, and a zoom operation button 36. The two types of bending operation knobs 27 are each connected to an operation wire and are used for left / right bending operation and up / down bending operation of the bending portion 22. The zoom operation button 36 is operated when changing the imaging magnification of the imaging unit 41. The zoom operation button 36 has a wide side button 36W for changing the imaging magnification to the wide side and a telephoto side button 36T for changing the imaging magnification to the telephoto side. In addition, the operation unit 18 is provided with a treatment tool introduction port 31 which is an entrance of a duct for inserting a treatment tool.

[0032] The universal cord 19 is a connection cord for connecting the endoscope 10 to the light source device 11. The universal cord 19 includes a signal cable (not shown), a light guide (not shown), and a fluid tube (not shown). In addition, a connector 34 to be connected to the light source device 11 is provided at the end of the universal cord 19.

[0033] The connector 34 is provided with, for example, a control board 46 for controlling the endoscope 10. When the connector 34 is connected to the light source device 11, the control board 46 is electrically connected to the light source device 11 and the processor device 12. As a result, the light source device 11 supplies the endoscope 10 with power, control signals, illumination light, gas, and water required for operating the endoscope 10. In addition, an image signal of the observation site acquired by the imaging unit 41 of the tip portion 23 is transmitted from the endoscope 10 to the light source device 11.

[0034] In addition, the control board 46 is provided with a motor control unit 47 that controls the DC motor 43. A signal line 38 that connects the motor control unit 47 and the DC motor 43 is disposed inside the universal cord 19. A drive signal is transmitted from the motor control unit 47 to the DC motor 43 through the signal line 38.

[0035] 2, the imaging unit 41 has an imaging element 48 and a zoom optical system 51 having a zoom function as a photographing optical system. The imaging element 48 and the zoom optical system 51 are arranged along an optical axis OA. The imaging element 48 is an image sensor having an imaging surface on which a plurality of pixels made up of photoelectric conversion elements are two-dimensionally arranged, and outputs an electrical signal representing a subject image formed on the imaging surface.

[0036] The zoom optical system 51 has, for example, an objective lens 51A and a variable magnification lens 51B. A light beam representing an object image to be observed is incident on the objective lens 51A. The objective lens 51A collects the incident light beam and forms an object image on the imaging surface of the imaging element 48. The variable magnification lens 51B is a movable lens for changing the shooting magnification of the zoom optical system 51. When the variable magnification lens 51B moves along the optical axis OA, the focal length of the zoom optical system 51 changes and the shooting magnification changes. The variable magnification lens 51B is provided so as to be freely movable between a wide end where the focal length is the shortest and the angle of view is the largest, and a telephoto end where the focal length is the longest and the angle of view is the smallest. At the wide end, the angle of view is wide but the shooting magnification is the smallest, and at the telephoto end, the angle of view is narrow but the shooting magnification is the largest. Although the zoom optical system 51 is shown as being composed of two lenses, this is merely a schematic diagram, and in reality, it is often composed of more than two lenses, and the variable magnification lens 51B may also be composed of multiple lenses.

[0037] The variable magnification lens 51B changes its lens position in the optical axis OA direction by the operation of the torque wire 42 and the cam shaft 52 connected to one end of the tip side of the torque wire 42. The cam shaft 52 is a shaft extending along the optical axis OA, and a cam groove 52A is formed on its circumferential surface. A cam pin 53 is provided on the lens holding frame of the variable magnification lens 51B, and the cam groove 52A and the cam pin 53 engage with each other. When the cam shaft 52 rotates around its axis due to the rotation of the torque wire 42, the engagement position between the cam pin 53 and the cam groove 52A is displaced along the optical axis OA direction, and the variable magnification lens 51B moves along the optical axis OA. For example, when the torque wire 42 rotates in the positive direction, the variable magnification lens 51B moves toward the telephoto end, and when the torque wire 42 rotates in the negative direction opposite to the positive direction, the variable magnification lens 51B moves toward the wide end.

[0038] The output shaft 45 of the reduction gear 44 is provided with a convex portion 45A that protrudes radially from a part of the outer circumferential surface. The output shaft 45 is provided with a contact portion 56 that contacts the convex portion 45A. The contact portion 56 regulates the rotation range of the output shaft 45 by contacting the convex portion 45A. The contact portion 56 is provided at two locations. The contact portion 56 sets the rotation range of the output shaft 45 within one rotation (i.e., 360°). This is to suppress twisting of the torque wire 42 by limiting the amount of rotation around the axis of the torque wire 42 to within one rotation. As an example, the rotation range of the output shaft 45 is in the range of 300° to 350°. The variable magnification lens 51B moves from the wide end to the telephoto end within the range of the amount of rotation of the output shaft 45 within one rotation. The rotation range of the torque wire 42 and the movement range MR of the variable magnification lens 51B are determined by the cam groove 52A.

[0039] As an example, the rotational position of the output shaft 45 when the variable magnification lens 51B is at the wide end is defined as the wide end position PW, and the rotational position of the output shaft 45 when the variable magnification lens 51B is at the tele end is defined as the tele end position PT. In this case, one of the two contact portions 56 restricts the rotation of the output shaft 45 by contacting the convex portion 45A of the output shaft 45 at the wide end position PW. The other contact portion 56 restricts the rotation of the output shaft 45 by contacting the convex portion 45A of the output shaft 45 at the tele end position PT. The wide end position PW and the tele end position PT are examples of the "first end position" and the "second end position" according to the technology of the present disclosure, respectively.

[0040] In this way, the torque wire 42 transmits the driving force of the DC motor 43 to the variable magnification lens 51B, and the reducer 44 is a reducer that reduces the rotation of the DC motor 43 and transmits it to the torque wire, and has an output shaft 45 connected to the torque wire 42 and rotates the torque wire 42 about its axis. The torque wire 42 and the reducer 44 are an example of a "driving force transmission mechanism" according to the technology of the present disclosure.

[0041] As shown in Fig. 3, the motor control unit 47 includes a processor 61, a drive circuit 62, a low-pass filter (LPF) 63, an analog-to-digital converter (ADC) 64, and a memory 65. The drive circuit 62 drives the DC motor 43 by outputting a drive pulse as a drive signal. The drive circuit 62 generates a drive pulse by repeating an application state in which a drive voltage VD (see Fig. 4) is applied between a pair of terminals 43A and 43B of the DC motor 43 and an open state in which the terminals 43A and 43B are opened. The drive circuit 62 drives the DC motor 43 in a pulse width modulation (PWM) mode in which the drive pulse is periodically input.

[0042] The drive circuit 62 has a switch circuit 66 that generates a drive pulse. As shown in FIG. 3, the switch circuit 66 has three contacts, a first contact 66A, a second contact 66B, and a third contact 66C. The first contact 66A is connected to the positive side of a power source 67, and the second contact 66B is connected to the negative side. The first contact 66A is connected to a terminal 43A of the DC motor 43, and the third contact 66C is connected to the other terminal 43B. One end of the switch 66D is connected to the third contact 66C.

[0043] 4, the state in which the other end of the switch 66D is connected to the second contact 66B is the applied state. In the applied state, the drive voltage VD of the power source 67 is applied between the terminals 43A and 43B of the DC motor 43. On the other hand, the state in which the other end of the switch 66D is not connected to either the first contact 66A or the second contact 66B is the open state. In the open state, the drive voltage VD of the power source 67 is not applied to the DC motor 43.

[0044] In the normal PWM mode, instead of the open state, a short-circuit state is used in which the other end of the switch 66D is connected to the first contact 66A, and a drive pulse is generated by repeating the applied state and the short-circuit state. In this respect, the PWM mode according to the technology of the present disclosure differs from the conventional PWM mode.

[0045] As shown in the time chart of the terminal voltage V generated at terminals 43A and 43B of the DC motor 43 in Fig. 4, the applied state and the open state are periodically repeated to generate a continuous driving pulse. The driving pulse is a rectangular wave with a wave height of the driving voltage VD. In the PWM mode, the duty ratio is changed by adjusting the pulse width W of the driving pulse in one period. The power supplied from the power source 67 to the DC motor 43 can be changed. Naturally, the wider the pulse width W, i.e., the longer the application period in which the applied state continues, the greater the supplied power.

[0046] As shown in the time chart of Fig. 4, in the open state, the drive voltage VD is not applied to the DC motor 43, but a counter electromotive force VL is generated in the DC motor 43 due to the self-induction action of the coil of the DC motor 43. As is well known, the counter electromotive force VL is a voltage generated in a direction that prevents a current change occurring in the coil of the DC motor 43. When the application section ends, the application of the drive voltage VD ends, so the current flowing through the coil of the DC motor 43 decreases, but the counter electromotive force VL is generated in a direction that prevents the current change. Therefore, the counter electromotive force VL is lower than the drive voltage VD, but generates a voltage in a direction that causes the DC motor 43 to continue rotating.

[0047] 4, the drop in the inter-terminal voltage V immediately after the driving pulse waveform falls is an overshoot. The driving voltage VD is inverted between positive and negative depending on the direction of rotation of the DC motor 43.

[0048] 4, the average voltage Vav is the average value of the drive voltage VD and the back electromotive force VL taking into account the time ratio within one period of the drive pulse. The average voltage Vav is defined as follows. Vav×(t1+t2)=VD×t1+VL×t2...Equation (1) From equation (1), Vav=(VD×t1+VL×t2) / (t1+t2)...Equation (2) Here, t1 and t2 are defined as follows. If the sum of t1 and t2 is the drive period of DC motor 43, t1 is the total time of the application section during which drive voltage VD is generated in the drive period, and t2 is the total time of the open section during which back electromotive force VL is generated in the drive period. The left side of equation (1) represents the power supplied to DC motor 43 in a certain drive period (t1+t2), and driving DC motor 43 in PWM mode using drive pulses of drive voltage VD is equivalent to driving DC motor 43 by continuously inputting average voltage Vav to it.

[0049] In reality, the counter electromotive force VL fluctuates during the drive period, so the counter electromotive force VL in the above formulas (1) and (2) is an average value during the drive period.

[0050] 3, the LPF 63 smoothes an input signal corresponding to the waveforms of the terminal voltage V of the DC motor 43, i.e., the drive voltage VD and the back electromotive force VL generated between the terminals 43A and 43B of the DC motor 43, and outputs an output signal of the smoothed average voltage Vav to the processor 61 via the ADC 64. The LPF 63 is a well-known LPF configured, for example, by an RC filter combining a resistor and a capacitor, or an LC filter combining an inductor and a capacitor.

[0051] The ADC 64 converts the analog signal of the average voltage Vav output by the LPF 63 into a digital signal, and outputs the converted digital signal of the average voltage Vav to the processor 61 .

[0052] The processor 61 is, for example, a microcomputer, and receives an operation signal from the zoom operation button 36. When the operation signal is input, the processor 61 outputs a command signal for commanding the start or stop of rotation of the DC motor 43 to the drive circuit 62. The drive circuit 62 starts or stops driving the DC motor 43 based on the command signal from the processor 61.

[0053] The processor 61 controls the position of the variable magnification lens 51B of the zoom optical system 51 based on the input operation signal. More specifically, the processor 61 performs step zoom control to change the position of the variable magnification lens 51B stepwise to a plurality of preset target positions, thereby changing the focal length of the zoom optical system 51 stepwise. When performing step zoom control, the variable magnification lens 51B must be moved to a target position and stopped at the target position, so it is necessary to control the amount of movement of the variable magnification lens 51B through control of the amount of rotation of the DC motor 43. The processor 61 controls the position of the variable magnification lens 51B based on a time integral value Q(VL) of the back electromotive force VL.

[0054] 5, the back electromotive force VL is correlated with the rotation speed ω of the DC motor 43, and as an example, the back electromotive force VL is proportional to the rotation speed ω of the DC motor 43. Therefore, the processor 61 can grasp the amount of rotation of the DC motor 43 by detecting the time integral value Q(VL) of the back electromotive force VL during driving, and as a result, it becomes possible to control the amount of movement of the variable magnification lens 51B.

[0055] As shown in FIG. 6, in this example, the processor 61 acquires an average voltage Vav obtained by averaging the drive voltage VD and the back electromotive force VL from the LPF 63, and calculates a time integral value Q(VL) of the back electromotive force VL based on the acquired average voltage Vav and a known drive pulse corresponding to the drive voltage VD. The memory 65 stores drive conditions for the PWM mode. The drive conditions for the PWM mode include the drive voltage VD and the pulse width W of the drive pulse. The processor 61 calculates the time integral value Q(VL) of the back electromotive force VL based on this information and the average voltage Vav, using formula (1). The time integral value Q(VL) of the back electromotive force VL is an integrated value of the time during which the back electromotive force VL is generated during the drive period of the DC motor 43.

[0056] As shown in FIG. 5, the back electromotive force VL represents the rotation speed of the DC motor 43, so the time integral value Q(VL) of the back electromotive force VL represents the amount of rotation of the DC motor 43, and as a result, the amount of movement of the magnification variable lens 51B.

[0057] Furthermore, lens target position information is stored in the memory 65. The lens target position information is a correspondence relationship between a plurality of step positions SP, which are target positions to which the variable magnification lens 51B is moved in step zoom, and a target value TQ(VL) of the time integral value for moving to each step position SP.

[0058] Fig. 7 is an example of lens target position information. In the example of Fig. 7, target values ​​TQ1(VL) to TQ5(VL) of the time integral value are associated with each of step positions SP1 to SP5. For example, step position SP1 is a position corresponding to the wide end of the magnification variable lens 51B, and step position SP5 is a position corresponding to the telephoto end of the magnification variable lens 51B.

[0059] Each of the target values ​​TQ1(VL) to TQ5(VL) is the amount of movement from a preset reference position. For example, when the reference position is step position SP1, the target value TQ1 is "0." The target value TQ2 corresponds to the amount of movement of the variable magnification lens 51B from step position SP1, which is the wide end, to step position SP2. The target value TQ3 corresponds to the amount of movement of the variable magnification lens 51B from step position SP1 to step position SP3. The same is true for the target values ​​TQ4 and TQ5.

[0060] Such lens target position information is created, for example, as follows. The DC motor 43 is driven to rotate the output shaft 45 from the wide end position PW to the tele end position PT. This rotation also moves the variable magnification lens 51B from the wide end to the tele end. The processor 61 measures the time integral value Q(VL) of the back electromotive force VL while driving the DC motor 43, and obtains the total time integral value Q(VL) from the wide end position PW to the tele end position PT. On the other hand, when the variable magnification lens 51B is moved from the wide end to the tele end, the correlation between the movement amount of the variable magnification lens 51B and the change amount of the focal length is known as design information of the zoom optical system 51. In other words, it is known how the focal length changes depending on the amount of movement. In addition, the focal length corresponding to each step position SP1 to SP5 is determined. If the total time integral value Q(VL) is known, it is possible to obtain the time integral value Q(VL) when the variable magnification lens 51B is moved from the reference position to each of the step positions SP1 to SP5. The time integral value Q(VL) of each of the step positions SP1 to SP5 is recorded as the respective target value TQ(VL).

[0061] In addition to the method of obtaining lens target position information based on the total time integral value Q(VL), the target value TQ(VL) of the time integral value corresponding to each step position SP1 to SP5 can also be obtained by the following method. That is, the focal length changes by moving the variable magnification lens 51B, but the focal length at the current position of the variable magnification lens 51B can be calculated backward from the size of the subject image formed on the image sensor 48 based on the imaging formula if the subject distance is known. Since the focal length of each step position SP1 to SP5 is determined, the position of the variable magnification lens 51B can be detected from the size of the subject image by calculating the focal length backward based on the position of the variable magnification lens 51B. By this method, the variable magnification lens 51B is moved to each step position SP1 to SP5, and the time integral value Q(VL) required to move the variable magnification lens 51B to each position is detected. Then, the detected time integral value Q(VL) of each step position SP1 to SP5 is recorded as the target value TQ(VL).

[0062] In this way, the lens target position information is a correspondence relationship between step positions SP1-SP5, which are multiple target positions of the variable lens 51B, and the time integral value Q(VL) of the back electromotive force VL required to move the variable lens 51B to each of the target positions SP1-SP5, i.e., the target value TQ(VL). The processor 61 controls the position of the variable lens 51B based on the lens target position information acquired from the memory 65.

[0063] In addition, since the DC motor 43 rotates in both the positive and negative directions, the time integral value Q(VL) of the back electromotive force VL is a positive value when rotating in the positive direction, and a negative value when rotating in the negative direction. The processor 61 grasps the current position of the magnification variable lens 51B using the time integral value QL(VL) of the back electromotive force VL. For example, when the magnification variable lens 51B moves from the wide end to the telephoto end based on the initial position of the magnification variable lens 51B, the processor 61 adds the time integral value Q(VL) of the positive back electromotive force VL. When the magnification variable lens 51B moves from the telephoto end to the wide end, the processor 61 adds the time integral value Q(VL) of the negative back electromotive force VL. In this way, if the initial position of the magnification variable lens 51B is set, the processor 61 can grasp the current position of the magnification variable lens 51B by using the time integral value Q(VL) of the back electromotive force VL.

[0064] A configuration in which the motor control unit 47, the DC motor 43, the reducer 44, the torque wire 42, and the cam shaft 52 are combined is an example of a "lens position control device" according to the technology of the present disclosure. In addition, the endoscope 10 to which this "lens position control device" is applied is an example of an "endoscopic device" according to the technology of the present disclosure.

[0065] The operation of the above configuration will be described with reference to the lens position control flow chart shown in Fig. 8. When the endoscope system 9 is started, the processor 61 starts the lens position control process. In step ST1101, the processor 61 waits for input of an operation signal by operating the zoom operation button 36. When an operation signal is input (Y in step ST1101), the process proceeds to step ST1102.

[0066] In step ST1102, the processor 61 determines the target position of the step zoom in response to the operation signal. For example, when the zoom operation button 36 is pressed once, the processor 61 determines that the step position SP, which is the step position SP moved by one step, is the target position of the step zoom. More specifically, for example, when the current position of the magnification variable lens 51B is at step position SP1, and the telephoto side button 36T is pressed once, the processor 61 determines that the step position SP2, which is moved one step from the step position SP1 to the telephoto side, is the target position.

[0067] Then, in step ST1103, the processor 61 acquires a target value TQ(VL) of the time integral value corresponding to the determined target position with reference to the lens target position information shown in Fig. 7. When moving from step position SP1 to step position SP2, the processor 61 acquires a target value TQ(VL) of the time integral value corresponding to step position SP2.

[0068] In step ST1104, the processor 61 starts driving, in PWM mode, the DC motor 43. In step ST1105, the processor 61 obtains the average voltage Vav while the DC motor 43 is being driven.

[0069] In step ST1106, the processor 61 calculates the time integral value Q(VL) of the back electromotive force VL based on the average voltage Vav in accordance with the procedure shown in FIG.

[0070] In step ST1107, the processor 61 compares the time integral value Q(VL) with the target value TQ(VL) and determines whether or not the two match. If the processor 61 determines that the two match (Y in step ST1107), it stops driving the DC motor 43 in step ST1108. This allows the variable magnification lens 51B to be moved to the step position SP according to the input operation signal.

[0071] As described above, the "lens position control device" according to the technology of the present disclosure that is applied to the endoscope system 9 includes a brushed DC motor 43 that generates a driving force for changing the position of the variable magnification lens 51B of the zoom optical system 51, a drive circuit 62 that drives the DC motor 43 by repeating an applied state in which a drive voltage is applied between a pair of terminals of the DC motor 43 and an open state in which the terminals are opened, and a processor 61 that controls the position of the variable magnification lens 51B based on a time integral value Q(VL) of the back electromotive force VL generated in the DC motor 43 in the open state. Therefore, compared to the conventional technology, it is possible to control the lens position with a simple configuration and high accuracy.

[0072] That is, first, since the DC motor 43, which is an example of a brushed DC motor, is used, the configuration of the DC motor 43 and the drive circuit 62 is simpler than when the three-phase brushless DC motor described in Patent Document 1 is used. Furthermore, since the position of the variable magnification lens 51B is controlled based on the time integral value Q(VL) of the back electromotive force VL, the accuracy of the control of the lens position is higher than that of the technology described in Patent Document 2 in which the amount of rotation of the DC motor is controlled by counting the drive time.

[0073] Even if the same driving pulse is applied to the DC motor 43, the rotation speed ω of the DC motor 43 varies when the load varies due to various factors. The various factors include a change in the resistance value of the DC motor 43 due to the ambient temperature, deterioration over time due to the progress of wear of the DC motor 43 and the reducer 44, and a change in the viscosity of the grease of the reducer 44 due to the ambient temperature or over time. However, since the back electromotive force VL has a correlation with the rotation speed ω of the DC motor 43 (proportional relationship as shown in FIG. 5 as an example), the time integral value Q(VL) of the back electromotive force VL for controlling the amount of rotation of the DC motor 43 and the corresponding amount of movement of the variable magnification lens 51B is a value that reflects the variation in the rotation speed ω caused by the load variation. Therefore, according to the lens position control device according to the technology disclosed herein, even if there is a variation in the rotation speed ω caused by the load variation, the position of the variable magnification lens 51B can be controlled with high accuracy.

[0074] This effect will be explained in more detail with reference to Fig. 9. As shown in Fig. 9, a state "A" where the load is relatively light is compared with a state "B" where the load is relatively heavy. In this case, in the state "A" where the load is light, the rotation speed ω of the DC motor 43 is fast and the back electromotive force VLa is also large. Conversely, in the state "B" where the load is heavy, the rotation speed ω of the DC motor 43 is slow and the back electromotive force VLb is also small.

[0075] In FIG. 9, the area of ​​each of the rectangles "A" and "B" is a value obtained by multiplying the back electromotive force VL proportional to the rotation speed ω by time, and therefore corresponds to the amount of rotation of the DC motor 43 and the corresponding amount of movement of the magnification variable lens 51B. The area of ​​the rectangle of "A" is the back electromotive force VLa x time ta, which corresponds to the time integral value Q(VLa) of the back electromotive force VLa. This time integral value Q(VLa) is the amount of rotation Ra of the DC motor 43 and corresponds to the amount of movement of the magnification variable lens 51B. The area of ​​the rectangle of "B" is the back electromotive force VLb x time tb, which corresponds to the time integral value Q(VLb) of the back electromotive force VLb. This time integral value Q(VLb) is the amount of rotation Rb of the DC motor 43 and corresponds to the amount of movement of the magnification variable lens 51B. The drive time ta of "A" is shorter than the drive time tb of "B".

[0076] Even when the same number of drive pulses are applied to the DC motor 43 at the same cycle, the rotation speed ω of the DC motor 43 fluctuates between "A" and "B" due to load fluctuations. Even in this case, the processor 61 controls using the time integral value Q(VL) of the back electromotive force VL, which has a correlation with the rotation speed ω, so that the amount of rotation of the DC motor 43 can be accurately grasped even when load fluctuations occur. This allows the lens position control device of the above embodiment to accurately grasp the amount of movement of the variable magnification lens 51B, and allows the lens position to be controlled with high precision.

[0077] The processor 61 also obtains an average voltage Vav obtained by averaging the drive voltage VD and the back electromotive force VL, and obtains a time integral value Q(VL) of the back electromotive force VL based on the average voltage Vav and a known drive pulse corresponding to the drive voltage VD. The average voltage Vav can be obtained relatively easily by using the LPF 64 or the like, so there are cases in which the advantage of a simplified configuration can be obtained by obtaining the time integral value Q(VL) from the average voltage Vav.

[0078] The lens position control device of the above embodiment also includes an LPF 43 that outputs to the processor an output signal of an average voltage Vav obtained by smoothing input signals corresponding to the waveforms of the drive voltage VD and the back electromotive force VL generated between the terminals of the DC motor 43. The LPF 43 can also remove noise from the signal waveform, improving the S (Signal) / N (Noise) ratio and enabling more accurate control of the lens position.

[0079] Furthermore, in the lens position control device of the above embodiment, the processor 61 performs step zoom control to change the position of the variable magnification lens 51B stepwise to a plurality of preset target positions, thereby gradually changing the focal length of the zoom optical system 51. When performing such step zoom control, precise control of the lens position is required, and therefore the technology of the present disclosure is particularly effective.

[0080] In the above embodiment, the processor 61 controls the position of the variable magnification lens 51B using table data such as the lens target position information shown in Fig. 7, which allows simpler processing than when the lens target position information is not used. Of course, the correspondence between the target positions such as the step positions SP1 to SP5 and the target value TQ(VL) of the time integral value, which is recorded as the lens target position information, does not have to be in the form of table data, and may be stored in the memory 65 in the form of a function.

[0081] Moreover, in the above embodiment, a driving force transmission mechanism including the torque wire 42 and the reduction gear 44 is used. By using the torque wire 42, such a driving force transmission mechanism can control the lens position of the zoom optical system 51 at the tip 23 of the small-diameter insertion section 17. In addition, the reduction gear 44 reduces twisting of the torque wire 42. Therefore, such a driving force transmission mechanism is effective for the endoscope 10.

[0082] 2, in the above embodiment, the variable magnification lens 51B moves from the wide-angle end to the telephoto end within one rotation of the output shaft 45. This can reduce the twisting of the torque wire 42.

[0083] (Modification of the first embodiment) 10, the processor 61 may monitor the value of the back electromotive force VL while driving the DC motor 43, and detect that the variable magnification lens 51B has reached the wide end or the telephoto end when the value of the back electromotive force VL reaches a value at which the DC motor 43 has stopped rotating. The premise for such end point detection is a configuration in which the output shaft 45 stops rotating by abutting against the abutment portion 56 at each of the wide end point position PW and the tele end point position PT, as shown in FIG.

[0084] When the output shaft 45 abuts against the abutment portion 56 while the DC motor 43 is being driven, the rotation of the DC motor 43 also stops. When the rotation of the DC motor 43 stops, the back electromotive force VL generated in the DC motor 43 naturally becomes "0". This value is an example of a value in a rotation stop state. By monitoring the back electromotive force VL, when the back electromotive force VL becomes "0", the processor 61 can determine that the variable magnification lens 51B has reached either the wide end end position PW or the telephoto end position PT. This determination enables the end point detection of the output shaft 45. Each end point position of the output shaft 45 corresponds to the wide end or telephoto end of the variable magnification lens 51B. Therefore, the processor 61 can detect that the variable magnification lens 51B has reached the wide end or telephoto end through the end point detection of the output shaft 45.

[0085] "Second embodiment" As in the second embodiment shown in Fig. 11, the drive circuit 62 may drive the DC motor 43 by repeating three states: an applied state, an open state, and a short-circuit state in which the terminals of the DC motor 43 are short-circuited. The short-circuit state is a state in which one end of the switch 66D is connected to the first contact 66A, and the terminals of the DC motor 43 are short-circuited. As shown in the time chart of Fig. 11, when the reference voltage is "0", the inter-terminal voltage V becomes "0" in the short-circuit state.

[0086] In the open section corresponding to the open state, although the back electromotive force VL is generated, the DC motor 43 is close to a state of rotating by inertia due to the inertial force generated in the application section. Therefore, in the open section, the rotation speed ω of the DC motor 43 is likely to fluctuate due to the load fluctuation. The fluctuation in the rotation speed ω affects the movement time of the magnification variable lens 51B.

[0087] On the other hand, in the short-circuit section corresponding to the short-circuit state, the DC motor 43 is in a state in which a brake is applied. Therefore, by adding a short-circuit state, it is possible to improve the load variation resistance (i.e., the resistance to load variations).

[0088] As shown in the upper time chart of Fig. 12, the load fluctuation resistance improves when the time ratio of the short circuit section is large. On the other hand, the time ratio of the open circuit section in which the back electromotive force VL is generated increases, so the S / N ratio of the back electromotive force VL signal improves.

[0089] In this way, even when short-circuit sections are mixed into the cycle of the drive pulse, there are advantages and disadvantages depending on the time ratio between the short-circuit section and the open-circuit section, so it is preferable to determine the time ratio taking these into consideration. As an example, it is preferable to set the time ratio of the short-circuit section in the range of 30% to 70% of the total time of the open-circuit section and the short-circuit section. This is because it is considered that a good balance can be secured between the load fluctuation resistance and the S / N ratio of the back electromotive force VL.

[0090] "Third embodiment" The third embodiment shown in Fig. 13 is an embodiment in which the back electromotive force VL is monitored and used for control. In the example shown in Fig. 10, the back electromotive force VL is used for end point detection. In the third embodiment, the back electromotive force VL is used for various controls, for example, various controls including speed control or abnormality detection.

[0091] In the third embodiment shown in Fig. 13, in order to actively use the back electromotive force VL for various controls, a circuit configuration is provided for detecting the back electromotive force VL instead of obtaining the back electromotive force VL from the average voltage Vav as in the first embodiment. Specifically, as shown in Fig. 13, an operational amplifier 71 is provided in addition to the LPF 63. The operational amplifier 71 receives the inter-terminal voltage V of the DC motor 43 at its non-inverting input terminal. Also, the output of the operational amplifier 71 is input to its inverting input terminal. This forms a voltage buffer circuit that reduces the influence caused by the difference in impedance between the input side and the output side of the operational amplifier 71.

[0092] An enable signal (indicated by EN in FIG. 13) is input from the processor 61 to the operational amplifier 71. The enable signal functions as a mask pattern for extracting the back electromotive force VL from the inter-terminal voltage V, as shown in FIGS. 14 and 15.

[0093] Fig. 14 is an example in which a mask pattern is applied to a drive circuit 62 that repeats two states, the applied state and the open state shown in Fig. 4 of the first embodiment. Fig. 15 is an example in which a mask pattern is applied to a drive circuit 62 that repeats three states, the applied state, the open state, and the short state shown in Figs. 11 and 12 of the second embodiment. In both cases, the signal of the back electromotive force VL is extracted by a mask pattern that is on (indicated by "1") in the open section.

[0094] An ADC 64 that converts the analog signal of the back electromotive force VL into a digital signal is provided in the subsequent stage of the operational amplifier 71, and the digital signal of the back electromotive force VL is input from the ADC 64 to the processor 61. The processor 61 monitors the value of this back electromotive force VL.

[0095] FIG. 16 shows an example in which the back electromotive force VL is used to control the speed of the DC motor 43. As shown in FIG. 16, the processor 61 compares the back electromotive force VL with a preset reference value while driving the DC motor 43. Then, based on the comparison result, the rotation speed ω of the DC motor 43 is controlled by adjusting the application time ratio of the drive voltage through the drive circuit 62. The larger the application time ratio of the drive voltage is, the larger the duty ratio is, and the smaller the application time ratio is, the smaller the duty ratio is. For example, when the back electromotive force VL falls below the reference value, the processor 61 increases the application time ratio of the drive voltage VD by widening the pulse width W of the drive pulse to control the rotation speed ω. This allows the rotation speed ω of the DC motor 43 to be increased.

[0096] Since the back electromotive force VL represents the actual rotation speed of the DC motor 43, highly accurate speed control is possible by controlling the rotation speed ω based on the back electromotive force VL.

[0097] 17 shows an example in which the back electromotive force VL is used for abnormality detection. In this case, a judgment condition for abnormality detection is stored in advance in the memory 65. Examples of abnormality detection include an abnormality in the DC motor 43 itself, and a break in the signal line 38 between the DC motor 43 and the drive circuit 62.

[0098] An abnormality of the DC motor 43 may be an abnormality caused by performance degradation of the DC motor 43. Factors that cause performance degradation of the DC motor 43 include an increase in sliding load due to wear of gears, bearings, brushes, and commutator, and the generation of oxide films, wear powder, foreign matter, etc. that occur between the brushes and commutator. These abnormalities can be detected based on the value of the back electromotive force VL.

[0099] For example, when an increase in the sliding load occurs, the rotation speed of the DC motor 43 decreases in the open section. Therefore, when a back electromotive force VL lower than the expected back electromotive force VL is detected, the processor 61 can determine that a load higher than expected is occurring in the DC motor 43. When the rotation of the DC motor 43 is locked and stopped due to an overload, the back electromotive force VL is not generated, and therefore the inter-terminal voltage V in the open section becomes "0".

[0100] Furthermore, when the signal line 38 between the drive circuit 62 and the DC motor 43 is broken, the terminal voltage V becomes a constant value according to the drive voltage VD due to the pull-down (or pull-up) resistor, regardless of whether it is an applied section or an open section. Therefore, the value of the counter electromotive force VL to be monitored also becomes a constant value according to the drive voltage VD. This value is significantly different from the value of the counter electromotive force VL detected under normal conditions, so that it is easy to detect the breakage. Furthermore, in the DC motor 43 with brushes, a momentary insulation state may occur due to a foreign object generated between the brushes and the commutator. Even in such an insulation state, the value of the counter electromotive force VL to be monitored becomes a constant value according to the drive voltage VD, so it is possible to detect it in the same way as a breakage.

[0101] 1, in the case of the endoscope 10, the signal line 38 is arranged in the universal cord 19 or the like, and therefore there is a risk of the signal line 38 being broken due to bending, etc. Therefore, such a technique is particularly effective in the case of the endoscope 10.

[0102] When the back electromotive force VL is used for abnormality detection in this way, a threshold value of the back electromotive force VL for determining an abnormality is stored in advance in the memory 65 as an abnormality determination condition. As shown in Fig. 17, while the DC motor 43 is being driven, the processor 61 determines whether the monitored back electromotive force VL matches the abnormality determination condition, and if it matches the abnormality determination condition, determines that an abnormality has occurred. If an abnormality has been determined, the processor 61 issues a warning to that effect. The warning may be displayed on the monitor 13 or may be issued through various indicators. Of course, it may also be issued by voice.

[0103] Furthermore, in the third embodiment, the back electromotive force VL is directly obtained by the operational amplifier 71, but the back electromotive force VL may be indirectly obtained from the average voltage Vav as in the first embodiment.

[0104] The various controls shown in the third embodiment can also be performed by comparing the average voltage Vav with a preset reference value. This is because the average voltage Vav is a value that reflects the back electromotive force VL. In this way, the method of using the average voltage Vav as it is can be considered as a method of indirectly using the back electromotive force VL. However, in this case, the S / N ratio of the signal value of the back electromotive force VL decreases. Therefore, the method of acquiring the back electromotive force VL by the operational amplifier 71 or the like as shown in the third embodiment, or the method of acquiring the back electromotive force VL by calculating it from the average voltage Vav as shown in the first embodiment, has a higher S / N ratio than the method of using the average voltage Vav as it is, and therefore enables more accurate control.

[0105] The above explanation can be used to understand the techniques described in the following supplementary paragraphs. <Additional notes 1> A lens position control device for controlling a position of a variable magnification lens of a zoom optical system provided in an endoscope, a brushed DC motor that generates a driving force for changing the position of the variable magnification lens; a drive circuit for driving the brushed DC motor by repeating a state in which a drive voltage is applied between a pair of terminals of the brushed DC motor and a state in which the terminals are opened; and a processor that controls the position of the variable magnification lens based on a time integral value of a back electromotive force generated in the brushed DC motor in an open state. Lens position control device. <Additional note 2> the processor obtains an average voltage by averaging the drive voltage and the back electromotive force, and obtains a time integral value of the back electromotive force based on the average voltage and a known drive pulse corresponding to the drive voltage; Item 1. A lens position control device according to claim 1. <Additional note 3> a low-pass filter that outputs an average voltage output signal obtained by smoothing an input signal corresponding to each waveform of the drive voltage and the back electromotive force generated between the terminals to a processor; Item 3. A lens position control device according to item 2. <Additional note 4> the processor controls step zooming, which changes the position of the variable magnification lens stepwise to a plurality of preset target positions, thereby changing the focal length of the zoom optical system stepwise; Item 3. A lens position control device according to any one of items 1 to 3. <Additional note 5> A correspondence relationship between a plurality of target positions of the variable magnification lens and a time integral value of the back electromotive force required to move the variable magnification lens to each target position is stored in advance in a memory; The processor controls the position of the magnification variable lens based on the correspondence obtained from the memory. 5. A lens position control device according to claim 4. <Additional note 6> A drive force transmission mechanism includes a torque wire that transmits the drive force of the brushed DC motor to the variable magnification lens, and a reducer that reduces the rotation of the brushed DC motor and transmits it to the torque wire, the reducer having an output shaft connected to the torque wire and rotating the torque wire around its axis. Item 5. A lens position control device according to any one of items 1 to 5. <Additional note 7> A variable magnification lens moves from the wide-angle end to the telephoto end within one rotation of the output shaft. 7. A lens position control device according to claim 6. <Additional Note 8> When the variable magnification lens is at one of the wide-angle end and the telephoto end, the rotational position of the output shaft is the first end point position, and when the variable magnification lens is at the other end, the rotational position of the output shaft is the second end point position. a contact portion that contacts the output shaft at each of the first end point position and the second end point position to restrict rotation of the output shaft; The processor monitors the back electromotive force while driving the brushed DC motor, and detects that the variable magnification lens has reached the wide-angle end or the telephoto end when the back electromotive force reaches a value corresponding to a state in which the brushed DC motor has stopped rotating. 8. A lens position control device according to claim 7. <Additional Note 9> The drive circuit drives a brushed DC motor by repeating three states: an applied state, an open state, and a short-circuit state in which the terminals are short-circuited. Item 8: A lens position control device according to any one of items 1 to 8. <Additional Note 10> The processor monitors the back electromotive force while driving the brushed DC motor and uses the back electromotive force for control. Item 9: A lens position control device according to any one of items 1 to 9. <Additional Note 11> The processor controls the rotation speed of the brushed DC motor by adjusting the ratio of the application time of the drive voltage through the drive circuit based on the result of comparing the back electromotive force with a preset reference value. Item 11. A lens position control device according to item 10. <Additional Note 12> The processor detects an abnormality including at least one of an abnormality of the brushed DC motor and a break in wiring between the drive circuit and the brushed DC motor based on the back electromotive force. Item 12. A lens position control device according to item 11. <Additional Note 13> An endoscope apparatus including an endoscope provided with a zoom optical system and a lens position control device that controls a position of a variable magnification lens of the zoom optical system, The lens position control device includes: a brushed DC motor that generates a driving force for changing the position of the variable magnification lens; a drive circuit for driving the brushed DC motor by repeating a state in which a drive voltage is applied between a pair of terminals of the brushed DC motor and a state in which the terminals are opened; and a processor that controls the position of the variable magnification lens based on a time integral value of a back electromotive force generated in the brushed DC motor in an open state. Endoscopic device.

[0106] In each of the above embodiments, for example, the hardware structure of a processing unit that executes various processes, such as the processor 61, may be any of the following processors. The various processors include a CPU (Central Processing Unit), which is a general-purpose processor that executes software to function as various processing units, a programmable logic device (PLD), which is a processor whose circuit configuration can be changed after manufacture, such as an FPGA (Field Programmable Gate Array), and / or a dedicated electric circuit, such as an ASIC (Application Specific Integrated Circuit), which is a processor having a circuit configuration designed specifically for executing specific processes.

[0107] A single processing unit may be configured with one of these various processors, or may be configured with a combination of two or more processors of the same type or different types (for example, a combination of multiple FPGAs and / or a combination of a CPU and an FPGA). In this way, the various processing units are configured using one or more of the various processors described above as a hardware structure.

[0108] Furthermore, more specifically, the hardware structure of these various processors can be an electric circuit that combines circuit elements such as semiconductor elements.

[0109] Furthermore, the technology of the present disclosure extends not only to the lens position control device and the endoscope device, but also to the operating program when these devices are realized by the operating program, and further extends to a computer-readable storage medium (such as a USB memory or a DVD (Digital Versatile Disc)-ROM (Read Only Memory)) that non-temporarily stores the operating program, in addition to the operating program.

[0110] The above description and illustrations are detailed descriptions of the parts related to the technology of the present disclosure, and are merely an example of the technology of the present disclosure. For example, the above description of the configuration, function, action, and effect is an example of the configuration, function, action, and effect of the parts related to the technology of the present disclosure. Therefore, it goes without saying that unnecessary parts may be deleted, new elements may be added, or replacements may be made to the above description and illustrations, within the scope of the gist of the technology of the present disclosure. In addition, in order to avoid confusion and to facilitate understanding of the parts related to the technology of the present disclosure, the above description and illustrations omit explanations of technical common sense that do not require explanation in order to enable the implementation of the technology of the present disclosure.

[0111] In this specification, "A and / or B" is synonymous with "at least one of A and B." In other words, "A and / or B" means that it may be only A, only B, or a combination of A and B. In addition, in this specification, the same idea as "A and / or B" is also applied when three or more things are expressed by connecting them with "and / or."

[0112] All publications, patent applications, and standards mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent application, and standard was specifically and individually indicated to be incorporated by reference. [Explanation of symbols]

[0113] 9,90 Endoscopy System 10 Endoscopy 11 Light source device 12 Processor Unit 13 Monitor 16 Observation images 17 Insertion section 18 Control section 19 Universal Code 21 Soft part 22 Curved section 23 Tip 27 Curvature control knob 28 Air / water supply button 29 Suction button 31 Treatment tool inlet 34 Connector 36 Zoom operation button 36T Telephoto button 36W Wide side button 38 Signal Line 41 Imaging unit 42 Torque Wire 43 DC motor (brushed DC motor) 43A, 43B terminals 44 Reducer 45 Output shaft 45A Convex 46 Control Board 47 Motor control unit 48 Image sensor 51 Zoom Optical System 51A Objective Lens 51B Variable Magnification Lens 52 Camshaft 52A Cam groove 53 Campin 56 Contact part 61 processors 62 Drive circuit 63 LPF 64 ADC 65 Memory 66 Switch Circuit 66A 1st contact 66B Second Contact 66C Third Contact 66D Switch 67 Power supply 71 Operational Amplifiers MR Movement Range V Terminal voltage Vav Average voltage VD Drive voltage VL, VLa, VLb Back electromotive force OA optical axis Q(VL), Q(VLa), Q(VLb) Time integral of back electromotive force Ra, Rb rotation amount SP, SP1~SP5 step positions TQ(VL), TQ1(VL)~TQ5(VL) Time integral target value W Pulse width t, t1, t2, ta, tb time ω rotation speed

Claims

1. A lens position control device for controlling a position of a variable magnification lens of a zoom optical system provided in an endoscope, a brushed DC motor that generates a driving force for changing the position of the variable magnification lens; a drive circuit for driving the brushed DC motor by repeating a state in which a drive voltage is applied between a pair of terminals of the brushed DC motor and a state in which the terminals are opened; a processor for controlling a position of the variable magnification lens based on a time integral value of a back electromotive force generated in the brushed DC motor in the open state. Lens position control device.

2. the processor obtains an average voltage by averaging the drive voltage and the back electromotive force, and obtains a time integral value of the back electromotive force based on the average voltage and a known drive pulse corresponding to the drive voltage. The lens position control device according to claim 1 .

3. a low-pass filter that outputs an average voltage output signal obtained by smoothing input signals corresponding to the waveforms of the drive voltage and the back electromotive force generated between the terminals to the processor; The lens position control device according to claim 2 .

4. the processor controls a step zoom for gradually changing a position of the variable magnification lens to a plurality of preset target positions, thereby gradually changing a focal length of the zoom optical system; The lens position control device according to claim 1 .

5. a correspondence relationship between a plurality of target positions of the variable magnification lens and a time integral value of the back electromotive force required for moving the variable magnification lens to each of the target positions is stored in a memory in advance; The processor controls a position of the variable magnification lens based on the correspondence relationship obtained from the memory. The lens position control device according to claim 4 .

6. a drive force transmission mechanism including a torque wire that transmits the drive force of the brushed DC motor to the variable magnification lens, and a reducer that reduces the rotation of the brushed DC motor and transmits it to the torque wire, the reducer having an output shaft connected to the torque wire and rotating the torque wire around its axis; The lens position control device according to claim 1 .

7. the variable magnification lens moves from a wide-angle end to a telephoto end within a range of one rotation of the output shaft; The lens position control device according to claim 6 .

8. When the rotation position of the output shaft when the variable magnification lens is at one of the wide end and the telephoto end is defined as a first end point position, and when the variable magnification lens is at the other end, the rotation position of the output shaft is defined as a second end point position, a contact portion that contacts the output shaft at each of the first end point position and the second end point position to restrict rotation of the output shaft, the processor monitors the back electromotive force while driving the brushed DC motor, and detects that the variable magnification lens has reached the wide-angle end or the telephoto end when the back electromotive force reaches a value corresponding to a state in which the brushed DC motor is stopped from rotating. The lens position control device according to claim 7 .

9. the drive circuit drives the brushed DC motor by repeating three states: the applied state, the open state, and a short-circuit state in which the terminals are short-circuited. The lens position control device according to claim 1 .

10. The processor monitors the back electromotive force while driving the brushed DC motor, and uses the back electromotive force for control. The lens position control device according to claim 1 .

11. the processor controls the rotation speed of the brushed DC motor by adjusting the ratio of the application time of the drive voltage through the drive circuit based on a comparison result between the back electromotive force and a preset reference value; The lens position control device according to claim 10 .

12. The processor detects, based on the back electromotive force, an abnormality including at least one of an abnormality of the brushed DC motor and a break in a wiring between the drive circuit and the brushed DC motor. The lens position control device according to claim 10 .

13. An endoscope apparatus including an endoscope provided with a zoom optical system and a lens position control device that controls a position of a variable magnification lens of the zoom optical system, The lens position control device includes: a brushed DC motor that generates a driving force for changing the position of the variable magnification lens; a drive circuit for driving the brushed DC motor by repeating a state in which a drive voltage is applied between a pair of terminals of the brushed DC motor and a state in which the terminals are opened; a processor for controlling a position of the variable magnification lens based on a time integral value of a back electromotive force generated in the brushed DC motor in the open state. Endoscopic device.

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