Endoscope apparatus

An endoscope apparatus has an endoscope and a video processor. The endoscope has a magnet and a coil, the magnet has a voice coil motor configured to be movable with respect to the coil and a Hall device disposed in the vicinity of the coil and configured to detect a magnetic field of the magnet in order to detect a position of the magnet. The video processor includes a position detection circuit configured to detect the position of the magnet from an outputted signal of the Hall device, an arithmetic operation section configured to correct a sensor output signal indicating the position of the magnet detected by the position detection circuit using correction information and output the sensor output signal, and a drive control circuit configured to control a current or a voltage to the coil based on an arithmetic operation result of the arithmetic operation section.

BACKGROUND OF INVENTION

1. Field of the Invention

The present invention relates to an endoscope apparatus and relates to an endoscope apparatus that has a drive mechanism using a voice coil motor.

2. Description of the Related Art

Endoscope apparatuses have been widely used in the medical field and the industrial field. In the medical field, for example, diseases are discovered and diagnosed by inserting elongated insertion sections into subjects and causing display devices to display endoscope images in the subjects.

There are endoscope apparatuses that have mechanisms configured to change image pickup magnification in order to observe subjects in an enlarged manner and perform focusing control.

For example, International Publication No. 2016/098225 proposes an endoscope that has an optical unit using a voice coil motor. The voice coil motor is used to drive a movable lens for focusing control, zooming control, and the like such that the movable lens moves forward and backward in an optical axis direction.

SUMMARY OF THE INVENTION

An endoscope apparatus according to an aspect of the invention includes: an endoscope; a voice coil motor provided in the endoscope and including a magnet and a coil such that the magnet is movable with respect to the coil; a magnetic sensor disposed in a vicinity of the coil and configured to detect a magnetic field of the magnet in order to detect a position of the magnet; a memory configured to store correction information; a position detection circuit configured to detect the position of the magnet from an outputted signal of the magnetic sensor; a processor configured to correct a position signal indicating the position of the magnet detected by the position detection circuit using the correction information stored in the memory and output the position signal; and a drive control circuit configured to control a current or a voltage to the coil based on an arithmetic operation result of the processor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG.1is a configuration diagram illustrating a configuration of an endoscope apparatus1according to the embodiment. As illustrated inFIG.1, the endoscope apparatus1according to the embodiment is configured to have an endoscope2and a video processor3to which the endoscope2is connected. A monitor4is connected to the video processor3.

The endoscope2is an electronic endoscope that has an elongated insertion section11, an operation section12connected to a proximal end of the insertion section11, and a universal cable13extending from the operation section12.

The insertion section11of the endoscope2has a rigid distal end portion21at a distal end of the insertion section11, a bending section22that is freely bent is provided so as to be adjacent to the distal end portion21, and a long flexible pipe section23is further provided on a side of the proximal end of the bending section22.

The distal end portion21incorporates an image pickup device34(FIG.2) and an optical unit51(FIG.3), which will be described later. The distal end portion21is provided with an observation window (not illustrated), and light from an object is incident on a light receiving surface of the image pickup device34through the observation window and an image pickup optical system35(FIG.2) of the optical unit51. The image pickup optical system35is an observation optical system that has a focusing control mechanism. An image pickup signal obtained by the image pickup device34is supplied to the video processor3via a signal line inserted into the insertion section11, the operation section12, and the universal cable13.

Note that various signal lines configured to deliver drive signals for a voice coil motor32(FIG.2) and a sensor section33(FIG.2), which will be described later, a position detection signal from the sensor section33, and the like are also inserted into the universal cable13.

Further, an illumination window (not illustrated) is also provided at the distal end portion21. Illumination light is emitted from the illumination window.

A user of the endoscope apparatus1can bend the bending section22in a desired direction by operating a bending knob24provided at the operation section12.

Various operation devices such as a release button are provided at the operation section12. A connector14is provided at a distal end of the universal cable13extending from the operation section12. The connector14is adapted to be able to be detachably attached to the video processor3.

The video processor3includes a light source device including a light source such as a lamp configured to generate illumination light, and the illumination light is incident on a proximal end surface of an optical fiber (not illustrated) inserted into the insertion section11, the operation section12, and the universal cable13and is then emitted from a distal end surface of the optical fiber disposed in the distal end portion21of the insertion section11. The illumination light emitted from the distal end surface of the optical fiber is emitted from the illumination window.

Note that the illumination light may be light of a light emitting element such as a light emitting diode (LED) incorporated in the distal end portion21.

The video processor3incorporates a control section configured to control the entire endoscope apparatus1. The user can perform various operations using various buttons of the operation section12, an operation panel3aof the video processor3, and the like. The video processor3executes programs in accordance with various functions in response to operations performed by the user.

The video processor3is a processor, to which an image pickup signal is inputted from the endoscope2to generate an endoscope image that is a subject image. An image signal of the endoscope image is outputted to the monitor4, and the endoscope image is displayed on the monitor4.

The video processor3has a focal point control section46(FIG.2) that controls a focusing position of a lens for focusing control of the image pickup optical system based on the endoscope image generated using the image pickup signal from the image pickup device34or based on a distance measurement signal included in the image pickup device34.

As described above, the endoscope apparatus1includes the endoscope2having an observation optical system having a lens driving mechanism and the video processor3that is a processor to which the endoscope2is connected.

FIG.2is a block diagram illustrating a configuration of the endoscope apparatus1.

The endoscope2has an image pickup section31, the voice coil motor (VCM)32that serves as an actuator, and the sensor section33. The image pickup section31, the voice coil motor32, and the sensor section33are provided in the distal end portion21of the insertion section11.

The image pickup section31has the image pickup device34such as a CCD image sensor and the image pickup optical system35. The image pickup optical system35is an optical system including a plurality of lenses and capable of adjusting a focus position and includes a lens35athat is a movable lens. AlthoughFIG.2illustrates only one lens35ain the image pickup optical system35, a plurality of movable lenses may be provided.

The image pickup device34receives light of an object image using a light receiving surface through the image pickup optical system35, performs photoelectric conversion, and outputs an image pickup signal to the video processor3. The image pickup optical system35, the voice coil motor32, and the sensor section33are disposed at an optical unit51(FIG.3) in the distal end portion21. A configuration of the optical unit51will be described later.

The voice coil motor32is an actuator provided in the endoscope2and configured to drive lenses related to the lens driving mechanism. Here, the voice coil motor32is provided in the distal end portion21and moves the lens35aalong an optical axis of the image pickup optical system35. The voice coil motor32is an electric actuator that is configured to include one or more coils and one or more magnets and that is driven by a drive current DI from the video processor3.

The voice coil motor32is of a so-called moving magnet type and has a structure in which the magnet is movable with respect to the coil.

The lens35ais fixed to a movable section53(FIG.3) on which a magnet section36(FIG.3) of the voice coil motor32is mounted. The lens35acan be moved in the optical axis direction of the image pickup optical system35by the voice coil motor32relatively moving the movable section53with respect to a coil section101(FIG.3) in the voice coil motor32. In other words, the voice coil motor32is of a moving magnet type that is provided in the endoscope2and has the magnet section36and the coil section101such that the magnet section36is movable with respect to the coil section101.

As described above, the voice coil motor32provided at the distal end portion21is an actuator that has the magnet section36(FIG.3) having one or more magnets and the coil section101(FIG.3) having one or more coils and that is capable of relatively moving the movable section53with respect to the coil section101.

Note that although the magnet section36is illustrated in the sensor section33inFIG.2, the magnet section36is a part of the voice coil motor32.

The sensor section33is a sensor provided in the endoscope2and configured to detect the position of the lens35arelated to a focus adjusting mechanism. Specifically, the sensor section33is configured to have a Hall device37and a differential amplifier38. The magnet section36includes eight magnets as will be described later. The magnet section36that configures the voice coil motor32is connected and fixed to the lens35a, and the magnet section36moves along with the lens35a.

The Hall device37is a sensor configured to be driven by a drive current IC from a constant current circuit43c, which will be described later, and detect a magnetic field of the magnet section36. The Hall device37that is a magnetic sensor is disposed in the vicinity of the coil section101and detects the magnetic field of the magnet section36in order to detect the position of the magnet section36.

The Hall device37outputs an analog signal in accordance with a magnitude of the detected magnetic field. Since the magnitude of the detected magnetic field changes in accordance with the position of the magnet section36, an outputted voltage of the Hall device37indicates the position of the magnet section36. Note that the sensor for position detection may be a magnetoresistive element instead of the Hall device37.

As described above, the sensor section33has the Hall device or the magnetoresistive element configured to detect a change in the magnetic field that accompanies movement of the lens35afor focusing control, and the Hall device or the magnetoresistive element receives supply of the drive current IC, which is a constant current, from the constant current circuit43c.

The differential amplifier38amplifies the analog signal from the Hall device37and outputs a sensor output signal PDa that is a voltage signal. In other words, the sensor section33outputs the sensor output signal PDa in accordance with the position of the lens35adriven by the voice coil motor32.

The voice coil motor32, the sensor section33, the image pickup optical system35, the Hall device37, and the differential amplifier38are included in the optical unit51(FIG.3).

The connector14of the universal cable13of the endoscope2incorporates a nonvolatile and rewritable memory39. The memory39stores correction information CI. The correction information CI is information for correcting influences of a magnetic field due to a magnetic flux leaking from the voice coil motor32in the sensor output signal PDa of the sensor section33. Since detection properties of the sensor section33vary for each endoscope due to component properties of the voice coil motor32, assembly errors, and the like, the correction information CI is information for cancelling the amount of error due to the leaking magnetic flux included in the sensor output signal PDa and is stored as individual information of the endoscope2in the memory39of the endoscope2.

Specifically, the correction information CI is used by an arithmetic operation section45, which will be described later, in order to correct the position of the magnet section36detected by the sensor section33. The memory39is a nonvolatile and rewritable memory such as a flash memory. Here, the memory39stores information regarding correction coefficients corresponding to coil currents as the correction information CI when the endoscope2is manufactured. The correction coefficients corresponding to coil currents are determined based on data actually measured for each endoscope.

When the endoscope2is connected to the video processor3, the correction information CI recorded in the memory39is read by the video processor3.

The video processor3has a voice coil motor (VCM) driver41, a drive control section42, a position detection section43, a current detection section44, the arithmetic operation section45, and the focal point control section46.

The video processor3has the control section (not illustrated) as described above. The control section includes a central processing unit (CPU), a ROM, a RAM, and the like and controls driving of the voice coil motor32in addition to overall operations of the endoscope apparatus1, generation of various images, and various kinds of processing in accordance with various functions. Programs for various kinds of processing are performed by executing programs stored in the ROM.FIG.2illustrates only a plurality of blocks related to the control of driving of the voice coil motor32.

The voice coil motor driver41is a circuit configured to generate the drive current DI for the voice coil motor32, output the drive current DI to the voice coil motor32, and also supply a current signal I indicating a current value of a current to be supplied to the voice coil motor32to the current detection section44.

The drive control section42is a circuit configured to generate a driving command signal DS and output the driving command signal DS to the voice coil motor driver41based on a focusing position command signal FC from the focal point control section46and lens position information PI from the arithmetic operation section45. Specifically, the drive control section42performs feedback control of the focusing position based on the lens position information PI from the arithmetic operation section45such that the lens35ais located at a focusing position designated through a command using the focusing position command signal FC, generates the driving command signal DS as a control signal, and outputs the driving command signal DS to the voice coil motor driver41.

The position detection section43is a position detection circuit including a power source43a, an analog-to-digital converter (hereinafter, abbreviated as an ADC)43b, and the constant current circuit43c.

The power source43ais a circuit configured to supply a power source voltage VC to the differential amplifier38via a signal line.

The ADC43bconverts the sensor output signal PDa that is an analog output from the differential amplifier38into a sensor output signal PDd that is a digital signal. The sensor output signal PDd indicates the position of the lens35a.

The constant current circuit43cis a circuit configured to supply the drive current IC, which is a constant current, to the Hall device37via a signal line.

The current detection section44is a circuit configured to detect the drive current DI outputted by the voice coil motor driver41. Specifically, the current signal I that is proportional to the drive current DI outputted by the voice coil motor driver41is inputted to the current detection section44, and the current detection section44outputs a digital current signal Id to the arithmetic operation section45.

The arithmetic operation section45is a circuit, into which the sensor output signal PDd from the position detection section43and the digital current signal Id from the current detection section44are inputted, which outputs the lens position information PI to the drive control section42.

Configurations of the position detection section43, the current detection section44, and the arithmetic operation section45will be described later.

The focal point control section46outputs the focusing position command signal FC for controlling the focusing position of the lens35afor the focusing control in the image pickup optical system based on the endoscope image generated from the image pickup signal from the image pickup device34or based on the distance measurement signal included in the image pickup device34as described above.

Next, a configuration of the optical unit disposed in the distal end portion21will be described.

FIG.3is an exploded perspective view illustrating a configuration of the optical unit51disposed at the distal end portion21of the insertion section11of the endoscope2according to the embodiment of the invention.FIG.4is a sectional view illustrating a configuration of main components in the optical unit51according to the embodiment.FIG.5is a sectional view of the optical unit51when seen in a cut plane passing through the line V-V inFIG.4.FIG.6is a sectional view of the optical unit51when seen in a cut plane passing through the line VI-VI inFIG.4. Note thatFIG.4is also a sectional view of the optical unit51when seen in a cut plane passing through the line IV-IV inFIG.5.

The optical unit51illustrated inFIGS.3to6includes a fixed section52, the movable section53that is movable with respect to the fixed section52, and the voice coil motor32that generates a drive force for causing the movable section53to move with respect to the fixed section52.

Hereinafter, a configuration of each component in the optical unit51will be described.

(Configuration of Fixed Section52)

The fixed section52has a front frame section54, a rear frame section55, a fixed section main body56, and a sensor section fixed section57. The sensor section33is provided so as to be fixed to the sensor section fixed section57. As illustrated inFIGS.5and6, the front frame section54holds an object-side fixed lens group Gf on a side closer to an object than a movable lens group Gv held by the movable section53and is attached to the fixed section main body56on the side of the object. The rear frame section55holds an image-side fixed lens group Gb on a side closer to an image than the movable lens group Gv and is attached to the fixed section main body56on the side of the image. Hereinafter, the side opposite to the side of the object along an axis C will be referred to as a side of the image.

First, a configuration of the fixed section main body56will be described.

(Configuration of Fixed Section Main Body56)

FIG.7is a perspective view illustrating a configuration of the fixed section main body56. The fixed section main body56illustrated in the drawing is a tubular-shaped member around a predetermined axis C. The fixed section main body56has a tubular section61having the axis C as a central axis and an image-side thick section62formed on the side of the image with respect to the tubular section61. The fixed section main body56has rotation symmetricity of 90° with respect to the axis C.

In the tubular section61, four punched sections61aare formed. Specifically, the four punched sections61arespectively penetrating through the tubular section61in the radial direction are formed at every 90° in the circumferential direction with respect to the central axis C in the longitudinal direction of the tubular section61. The respective punched sections61aare formed in plane sections61a1formed on an outer circumferential surface of the tubular section61parallel to the central axis C. The four plane sections61a1are also provided at every 90° in the circumferential direction with respect to the central axis C in the longitudinal direction of the tubular section61.

A surface inside the tubular section61in the radial direction except for the four punched sections61ais a tubular-shaped cylindrical surface and serves as a fixed-side sliding surface63configured to support and guide the movable section53. The fixed-side sliding surface63has a shape divided in the circumferential direction with the four punched sections61a.

The coil section101of the voice coil motor32is fixed to the outer circumferential portion of the tubular section61as illustrated inFIGS.4to6. Thus, the coil section101is fixed to the fixed section52.

The image-side thick section62is formed so as to project outward beyond the tubular section61in the radial direction. In the fixed-side sliding surface63inside the image-side thick section62in the radial direction, four grooves62aare formed. When the movable section53is assembled, plurality of magnets of the magnet section36, which will be described later, pass through the four grooves62a. Therefore, it is possible to smoothly assemble the movable section53with the fixed section main body56. Note that a structure in which the image-side thick section62is formed separately from the tubular section61and is attached to the tubular section61at the time of assembly may also be employed.

Next, a configuration of the front frame section54will be described.

(Configuration of Front Frame Section54)

FIGS.8A and8Bare perspective views illustrating a configuration of the front frame section54and perspective views when seen from different sides of the axis C, respectively. Note that the central axis of the front frame section54is referred to as the axis C because the central axis coincides with the central axis of the fixed section main body56at the time of assembly.

The front frame section54is a tubular-shaped member that has an outer circumferential portion71and an inner circumferential portion72. The outer circumferential portion71has a first outer circumferential portion71a, a second outer circumferential portion71b, and an outer circumference-side projecting portion71c. The inner circumferential portion72has a first inner circumferential portion72a, a second inner circumferential portion72b, and an inner circumference-side projecting portion72c.

In the outer circumferential portion71, the diameter of the first outer circumferential portion71ais larger than the diameter of the second outer circumferential portion71b. The outer circumference-side projecting portion71cwith the largest diameter projecting outward in the radial direction is provided between the first outer circumferential portion71and the second outer circumferential portion71b.

In the inner circumferential portion72, the diameter of the first inner circumferential portion72ais larger than the diameter of the second inner circumferential portion72b. The inner circumference-side projecting portion72cwith the smallest diameter projecting inward in the radial direction is located between the first inner circumferential portion72aand the second inner circumferential portion72b.

The front frame section54holds the object-side fixed lens group Gf. The object-side fixed lens group Gf has a first front lens Lf1and a second front lens Lf2aligned in this order from the side of the object. The first inner circumferential portion72aholds the first front lens Lf1, and the second inner circumferential portion72bholds the second front lens Lf2. An image-side outer edge portion of the first front lens Lf1and an object-side outer edge portion of the second front lens Lf2preferably abut on the inner circumference-side projecting portion72cas illustrated inFIGS.5and6.

When the front frame section54is inserted into the fixed section main body56, the front frame section54is inserted until an end surface61bof the fixed section main body56on the side of the object comes into contact with a step portion71dbetween the second outer circumferential portion71band the outer circumference-side projecting portion71cwhile the second outer circumferential portion71bis brought into contact with the fixed-side sliding surface63of the tubular section61of the fixed section main body56. In this manner, the front frame section54is inserted into the fixed section main body56and is fixed to the fixed section main body56with an adhesive or the like.

Next, a configuration of the rear frame section55will be described.

(Configuration of Rear Frame Section55)

FIGS.9A and9Bare perspective views illustrating a configuration of the rear frame section55and perspective views when seen from different sides of the axis C, respectively. Note that the central axis of the rear frame section55is referred to as the axis C because the central axis coincides with the central axis of the fixed section main body56at the time of assembly similarly to the front frame section54. The rear frame section55is a tubular-shaped member that has an outer circumferential portion81and an inner circumferential portion82. The outer circumferential portion81has a first outer circumferential portion81a, a second outer circumferential portion81b, and a third outer circumferential portion81c. The inner circumferential portion82has a first inner circumferential portion82a, a second inner circumferential portion82b, and an inner circumference-side projecting portion82c.

In the outer circumferential portion81, the diameter of the first outer circumferential portion81ais smaller than the diameter of the second outer circumferential portion81b, and the diameter of the second outer circumferential portion81bis smaller than the diameter of the third outer circumferential portion81c.

In the inner circumferential portion82, the diameter of the first inner circumferential portion82ais smaller than the diameter of the second inner circumferential portion82b. The inner circumference-side projecting portion82cwith the smallest diameter projecting inward in the radial direction is provided at an end portion of the first inner circumferential portion82aon the side of the object.

The rear frame section55holds the image-side fixed lens group Gb. The image-side fixed lens group Gb has a first rear lens Lb1and a second rear lens Lb2. The first inner circumferential portion82aholds the first rear lens Lb1and the second rear lens Lb in this order from the side of the object. The first rear lens Lb1on the side of the object preferably abuts on the inner circumference-side projecting portion82cas illustrated inFIGS.5and6.

When the rear frame section55is inserted into the fixed section main body56, the rear frame section55is inserted until an end surface62bof the fixed section main body56on the side of the image comes into contact with a step portion81dbetween the second outer circumferential portion81band the third outer circumferential portion81cwhile the second outer circumferential portion81bis brought into contact with the fixed-side sliding surface63of the image-side thick section62of the fixed section main body56.

Next, a configuration of the sensor section fixed section57that is a sensor fixed member will be described.

(Configuration of Sensor Section Fixed Section57)

FIG.10is a perspective view illustrating a configuration of the sensor section fixed section57. The sensor section fixed section57illustrated in the drawing is a tubular-shaped member around the predetermined axis C. The sensor section fixed section57has a tubular section95around the axis C as the central axis and a sensor mounting section96projecting in the outer diameter direction from the outer circumferential surface of the tubular section95.

The sensor section fixed section57has a tubular shape into which the fixed section main body56is inserted along the central axis C. The tubular section95and the sensor mounting section96are integrally formed.

A step portion95a2on which the coil section101abuts when the coil section101of the voice coil motor32is inserted into the tubular section95from the side of the image is formed in an inner circumferential surface95a1of the tubular section95.

The sensor mounting section96has a rectangular parallelepiped shape and has an elongated groove section96aformed along the axis C and opened in the outer diameter direction of the tubular section95. The groove section96ahas a shape with a wall section96a1on the side of the object and with no wall section on the side of the image.

Three holes96c,96d, and96eare formed in a bottom portion96bof the elongated groove section96ain this order from the side of the object.

The sensor section33is mounted in and fixed to the groove section96aof the sensor mounting section96.

Next, a configuration of the sensor section33will be described.

FIG.11is a perspective view of the sensor section33.

The sensor section33includes the Hall device37that serves as a magnetic sensor and a circuit board58aon which the Hall device37is mounted. The differential amplifier38is also mounted on the circuit board58a. The circuit board58ais disposed in the groove section96aof the sensor mounting section96and has an elongated shape with which the circuit board58acan be fixed to the bottom portion96b.

The circuit board58ais fixed to the inside of the groove section96awith an adhesive or the like such that the Hall device37enters the hole96d. The position of the hole96ddefines the position of the Hall device37. In other words, the hole96dis a hole for positioning the Hall device37.

As illustrated inFIG.4, the hole96dis formed at a position that faces magnets36aand36bof the magnet section36of the movable section53when the optical unit51is seen along the axis C from the side of the object.

Although a configuration of the movable section53will be described later, the movable section53has the magnet section36of the voice coil motor32and moves forward and backward in the axis C direction. The hole96dis formed such that, in defining the position of the end surface of the magnet section36on the side of the object when the movable section53moves closest to the side of the object as P1and the position of the end surface of the magnet section36on the side of the image when the movable section53moves closest to the side of the image as P2, the Hall device37is located within a range M between the positions P1and P2in the axis C direction.

FIG.12is a diagram for explaining a moving range of the magnet section36. The magnet section36has the plurality of magnets36aand36bas will be described later. InFIG.12, g1 represents the position of the magnet section36when the magnets36aand36bof the magnet section36have moved closest to the side of the object. Likewise, g2 represents the position of the magnet section36when the magnets36aand36bof the magnet section36have moved closest to the side of the image. The hole96dis formed such that the Hall device37is located within the range M between the position P1and the position P2in the axis C direction.

In other words, the Hall device37that is a magnetic sensor is located between the end surface of the magnet section36on the side in the moving direction of the magnet36awhen the magnet section36has moved in the direction on the side of the object along the central axis C and the end surface of the magnet section36on the side in the moving direction of the magnet36bwhen the magnet section36has moved in the direction on the side of the image, which is a direction opposite to the direction on the side of the object, along the central axis C.

Each of the holes96cand96eis a hole for coil wires. The coil wires are electric wires for the coil of the coil section101. The hole96cis a hole for extracting two coil wires (not illustrated) of a first coil101aof the coil section101, which will be described later, from the inside to the outside of the tubular section95as illustrated inFIG.5. The hole96eis a hole for extracting two coil wires101b1(FIGS.4and5) of second coil101bof the coil section101, which will be described later, from the inside to the outside of the tubular section95.

As described above, the coil section101is disposed at an outer circumferential portion of the fixed section main body56. Since the fixed section main body56is disposed inside the sensor section fixed section57, the coil section101is disposed inside the sensor section fixed section57. The holes96cand96efor allowing the coil wires of the coil section101to pass are formed in the sensor section fixed section57.

The two coil wires101a1of the first coil101aand the two coil wires101b1of the second coil101bare connected to a wiring pattern for a coil current line on the circuit board58a. The Hall device37and a wiring pattern of the differential amplifier38are also provided independently from the coil current line on the circuit board58a.

A distal end of a signal cable58bis soldered at an end of the circuit board58aon the side of the image. The signal cable58bis inserted into the insertion section11of the endoscope2.

An elongated urging plate59is provided so as to cover the groove section96aof the sensor mounting section96as illustrated inFIGS.3and5. The urging plate59is a rectangular plate-shaped magnetic body and is, for example, a cold rolled steel plate.

A step portion96ffor positioning the urging plate59is formed at a peripheral portion of the groove section96aof the sensor mounting section96on a side of the opening. The step portion96fis formed such that the distance from the axis C to the peripheral portion of the groove section96aon the side of the opening is shorter on the side of the object than on the side of the image. The urging plate59is fixed to the sensor mounting section96with an adhesive or the like such that an end on the side of the image abuts on the step portion96fand covers the groove section96a.

The length of the urging plate59in the axis C direction is equal to or greater than the aforementioned range M between the positions P1and P2, and the urging plate59is disposed to include the range between the positions P1and P2in the axis C direction when the urging plate59is fixed to the sensor mounting section96.

The magnets36aand36bof the movable section53are constantly equally attracted toward the side of the urging plate59by providing the urging plate59in this manner.

In other words, the urging plate59as an urging member that is a magnetic body is provided at the sensor section fixed section57, and the urging plate59is disposed at the sensor section fixed section57so as to attract the magnet section36in the outer diameter direction of the sensor section fixed section57.

Even if there is a gap between the inner circumferential surface of the fixed section main body56and the outer surface of the magnet section36of the movable section53in the fixed section main body56of the fixed section52, an increase in inclination of the movable section53with respect to the axis C is curbed since the magnets36aand36bare attracted to the urging plate59.

Motion of the movable section53along the axis C is stabilized, and it is also possible to prevent degradation of accuracy of position detection performed by the sensor section33, by providing such an urging plate59.

Since the urging plate59functions as a yoke of the magnet section36, there is also an effect of increasing a magnetic force of the magnet section36. As a result, it is possible to increase the outputted signal of the Hall device37, and an effect that accuracy of position detection can be improved is also achieved.

The respective components of the fixed section52with the aforementioned configuration are configured using materials that are non-magnetic bodies but have relative magnetic permeability of greater than 1.0, for example. Examples of such materials include austenite-based stainless steel.

Next, a configuration of the movable section53that is a movable member will be described.

FIG.13is a perspective view illustrating a configuration of the movable section53. The movable section53illustrated in the drawing includes a tubular-shaped member that has an outer circumferential portion91and an inner circumferential portion92. Hereinafter, the central axis of the movable section53will also be referred to as an axis C. This is because the central axis of the movable section53coincides with the central axis of the fixed section main body56at the time of assembly.

The outer circumferential portion91has a tubular section91aand two projecting edge portions91bformed at both end portions of the tubular section91ain the axis C direction and having a larger outer circumferential diameter than the diameter of the tubular section91a. The tubular section91aand the projecting edge portions91bmay be configured as an integrated member or may be configured as separate members.

Each projecting edge portion91bhas movable-side sliding surfaces91cformed of an outer circumferential surface of the projecting edge portion91band plane portions91dthat are formed at a part of the projecting edge portion91blocated outward in the radial direction. In the case illustrated inFIG.13, each projecting edge portion91balternately has four movable-side sliding surfaces91cand four plane portions91din the circumferential direction around the axis C at equal intervals. Each of the plane portions91dlies in the same plane as respective one of four plane portions91dformed on the side of the other end along the axis C. In other words, the outer circumferential portion91have four sets of two plane portions91dthat are formed at mutually different end portions and lie in the same plane.

In each of three sets out of the four sets, a step portion91ethat is formed inward in the radial direction as compared with the tubular section91aand has a plane-shaped outer circumferential surface is provided between the two plane portions91d. A notch portion91fwith a plane-shaped outer circumference is provided by chipping the surface of the tubular section91aat the center of the step portion91e, which is formed between the two plane portions91din each set, in the axis C direction.

A step portion91gwith a plane-shaped outer circumferential surface is also provided between the two plane portions91dof the remaining one set out of the four sets by being formed inward in the radial direction as compared with the tubular section91a. A rotation restricting section91hconfigured to restrict rotation of the movable section53about the axis C is provided at the center of the step portion91gin the axis C direction so as to project from the outer circumferential surface of the step portion91g.

A part of a side surface of the rotation restricting section91hthat comes into contact with the fixed section52has a bent R shape while side surfaces that respectively face the first magnet36aand the second magnet36bhave plane shapes. In other words, the surface of the projecting surface of the rotation restricting section91hthat is parallel to the axis C has a shape obtained by respectively chipping a circle with straight lines in a direction that perpendicularly intersects with the axis C on the side of the object and on the side of the image of the axis C and has a shape surrounded by two arcs and two straight lines. Note that the surface of the rotation restricting section91hthat is parallel to the axis C may have a circular shape with a diameter of the length of the rotation restricting section91hin the axis C direction illustrated inFIG.13. Alternatively, the surface of the rotation restricting section91hthat is parallel to the axis C may have a rectangular shape.

As illustrated inFIG.4, the width of the plane of the rotation restricting section91hthat is perpendicularly intersects with the axis C in the circumferential direction is greater than the width of each of the magnets36aand36b(the second magnet36bis illustrated inFIG.4) in the circumferential direction in the same plane.

The inner circumferential portion92has a first inner circumferential portion92a, a second inner circumferential portion92b, a third inner circumferential portion92c, and an inner circumference-side projecting portion92d. The diameter of the second inner circumferential portion92bis smaller than diameters of the first inner circumferential portion92aand the third inner circumferential portion92c. The inner circumference-side projecting portion92dwith the smallest diameter projecting inward in the radial direction is provided between the second inner circumferential portion92band the third inner circumferential portion92c.

The movable section53holds the movable lens group Gv. Specifically, the second inner circumferential portion92bof the movable section53holds a first movable lens Lv1that the movable lens group Gv has. As illustrated inFIGS.5and6, the first movable lens Lv1on the side of the image preferably abuts on the inner circumference-side projecting portion92d.

The movable section53is inserted into the fixed section main body56with the movable-side sliding surfaces91cbeing brought into contact with the fixed-side sliding surface63. As illustrated inFIGS.5and6, the movable section53is inserted such that the inside of the third inner circumferential portion92cin the radial direction faces the first outer circumferential portion81aof the rear frame section55. In this manner, at least a part of the image-side fixed lens group Gb is present inside the third inner circumferential portion92cof the movable section53in the radial direction. In the embodiment, in a case in which the movable section53has moved closest to the side of the object, at least a part of the object-side fixed lens group Gf is present inside the first inner circumferential portion92aof the movable section53in the radial direction.

As described above, the movable section53has a tubular shape, is disposed inside the fixed section main body56, is movable along the central axis C of the tubular-shaped fixed section main body56, and holds one lens or two or more lenses. The magnet section36is provided at the movable section53.

The movable section53with the aforementioned configuration is configured using a material such as stainless steel, aluminum, or a resin, for example.

(Configuration of Voice Coil Motor32)

Next, a configuration of the voice coil motor32will be described. The voice coil motor32has the coil section101disposed at the fixed section main body56of the fixed section52and the magnet section36disposed at the movable section53so as to face the inner circumferential portion of the coil section101, as illustrated inFIG.3.

The coil section101is formed by winding coil wires around the outer circumferential portion of the fixed section main body56.

Specifically, the coil section101has the first coil101aformed by winding coil wires around an outer circumference of the tubular section61of the fixed section main body56and the second coil101bdisposed so as to be aligned with the first coil101aalong the axis C and formed by winding coil wires around the outer circumference of the tubular section61of the fixed section main body56as illustrated inFIGS.5and6. Note that the coil section101wound in advance may be disposed later. The first coil101aand the second coil101bthat are adjacent to each other along the axis C are preferably connected in series but may be connected in parallel.

The first coil101aand the second coil101bhave plane portions101apand101bpthat face the punched sections61ain the fixed section main body56, respectively, as illustrated inFIG.5. The first coil101aand the second coil101balso have cylindrical portions101atand101btthat face the tubular section61, respectively, as illustrated inFIG.6. At the first coil101a, the four plane portions101apand the four cylindrical portions101atare alternately disposed in a section that perpendicularly intersects with the axis C. Similarly, the four plane portions101bpand the four cylindrical portions101btare alternately disposed in a section that perpendicularly intersects with the axis C at the second coil101bas well (seeFIG.4).

The magnet section36has four sets each including one first magnet36aand one second magnet36bdisposed so as to face the plane portions101apand101bpand aligned along the axis C inside the plane portions101apof the first coil101aand the plane portions101bpof the second coil101bas illustrated inFIGS.3to6. The first magnet36aand the second magnet36bin each set are disposed so as to be aligned along the axis C.

The four first magnets36aand the four second magnets36bin the four sets aligned along the axis C are disposed at equal intervals at every 90 degrees in the circumferential direction in the section that perpendicularly intersects with the axis C. The rotation restricting section91his located between the first magnet36aand the second magnet36bof one set out of the four sets.

It is possible to stably place the first magnets36aand the second magnets36bby employing such disposition. As a result, the voice coil motor32forms a stable magnetic field, and it is possible to curb deviation of the movable section53configured to move with respect to the fixed section52. Note that although the magnets36aand36bare placed at every 90° around the axis C in the embodiment, the magnets36aand36bmay be placed at other angular intervals.

As illustrated inFIGS.5and6, the total of the widths of the first magnets36aand the second magnets36bin the axis C direction is shorter than the total of the widths of the first coil101aand the second coil101bin the axis C direction. In this manner, it is possible to allow the first magnets36aand the second magnets36bto be present within the widths of the first coil101aand the second coil101bin the axis C direction, respectively, within the moving range of the movable section53.

FIG.14is a diagram illustrating a configuration of only the voice coil motor when seen in the cut plane passing through the line XIV-XIV illustrated inFIG.5.FIG.15is a diagram illustrating only the voice coil motor in the same section as that inFIG.5.

As illustrated inFIG.15, the first magnet36aand the second magnet36bin a set are disposed away from each other along the axis C. Further, as illustrated inFIGS.14and15, the magnet section36has a plurality of magnets disposed at equal angles around the central axis C, and the respective magnets have undergone magnetic polarization in the direction that perpendicularly intersects with the central axis C. The first magnet36aand the second magnet36bin each set are respectively magnetized in the radial direction, and magnetic poles are directed in opposite directions from each other.

In the case illustrated inFIGS.14and15, the four first magnets36ahave N poles on the side of the first coil101aand S poles on the opposite side, and the four second magnets36bhave S poles on the side of the second coil101band N poles on the opposite side. In this case, the magnetic polarization direction of the first magnet36aand the second magnet36bin each set perpendicularly intersect with the axis C as represented by the arrow A illustrated inFIGS.14and15. Note that more generally, the magnetic polarization direction of the first magnet36aand the second magnet36bin each set may be any direction as long as the direction intersects the axis C.

As illustrated inFIG.4, the Hall device37that is a magnetic sensor is disposed outside the coil section101in the radial direction so as to face at least one of the plurality of magnets.

In the embodiment, a winding direction of the coil section101is preferably inverted between the set of first magnets36aand the set of second magnets36bin the respective sets. In a case in which the first coil101ais wound in the direction of the arrow B as illustrated inFIG.14, the second coil101bmay be wound in the opposite direction. Alternatively, the winding directions of the first coil101aand the second coil101bmay be the same, and the first coil101aand the second coil101bmay be connected such that current directions are opposite. In this case, it is only necessary for the current to flow in the direction opposite to the arrow B to the second coil101bwhen the current directed as the arrow B is caused to flow through the first coil101aas illustrated inFIG.14.

As described above, the coil section101has the first coil101aand the second coil101baligned along the central axis C. The magnet section36includes the plurality of first magnets36adisposed inside the first coil101ain the circumferential direction and the plurality of second magnets36bdisposed inside the second coil101bin the circumferential direction. The magnetic polarization direction of the plurality of first magnets36aand the magnetic polarization direction of the plurality of second magnets36bare opposite to each other, and the first coil101aand the second coil101bare connected such that directions of the supplied current are inverted.

In the optical unit51with the aforementioned configuration, the movable section53on which the four magnets36aare respectively placed so as to face the first coil101ais disposed inside the fixed section main body56, around which the first coil101ais wound, in the radial direction. Therefore, the plane portions101apof the first coil101aare respectively present in the magnetic field in directions that perpendicularly intersects the surfaces111aoutside the first magnets36ain the radial direction. Note that the four second magnets36bare also configured in a similar manner.

Therefore, driving efficiency is improved, and it is possible to quickly move the movable section53. In addition, it is possible to easily assemble the optical unit51by forming the surfaces111aoutside the first magnets36ain the radial direction and the surfaces111boutside the second magnets36bin the radial direction into plane shapes.

If a current is caused to flow through the coil section101of the optical unit51, a force in the axis C direction is generated in the movable section53due to influences of the magnetic field of the magnet section36, and the movable section53moves in the axis C direction with respect to the fixed section52. It is possible to cause the movable section53to move with respect to the fixed section52by controlling currents to be caused to flow through the first coil101aand the second coil101b, respectively, for example. Even in a state where the movable section53moves with respect to the fixed section52, the outer surface of the magnet section36in the radial direction is disposed in the punched sections61aof the fixed section main body56.

The outer circumferential surfaces of the projecting edge portions91bof the movable section53configure the movable-side sliding surfaces91cthat come into contact with the fixed-side sliding surface63of the fixed section main body56in the optical unit51as illustrated inFIG.6. It is possible to cause the movable section53to move with respect to the fixed section main body56in a state in which the movable section53is constantly in contact with the fixed section main body56, to curb inclination of the movable section53with respect to the fixed section52, and to cause the movable section53to appropriately move by bringing the fixed-side sliding surface63of the fixed section main body56and the movable-side sliding surfaces91cof the movable section53into contact with each other.

(Position Control of Movable Section)

Next, a method for controlling the position of the movable section will be described.

FIG.16is a block diagram illustrating configurations of the position detection section43, the current detection section44, and the arithmetic operation section45in the video processor3.

The position detection section43detects the position of the magnet section36based on the outputted signal of the sensor section33. The position detection section43is a circuit that includes an analog-to-digital conversion circuit (hereinafter, referred to as an ADC)43band an analog low pass filter (LPF)43dthat has a predetermined cutoff frequency.

The analog low pass filter43dreceives the sensor output signal PDa from the sensor section33and outputs a signal at a predetermined low frequency to the ADC43b. The ADC43bconverts the voltage of the inputted signal into a digital signal and outputs the digital signal as the sensor output signal PDd to the arithmetic operation section45.

The current detection section44detects the magnitude of the current flowing through the coil section101. Therefore, the current detection section44is a circuit including an analog low pass filter (LPF)44athat has a predetermined cutoff frequency and an ADC44b.

The analog low pass filter44areceives the current signal I from the voice coil motor32and outputs a signal at a predetermined low frequency to the ADC44b. The ADC44bconverts the voltage of the inputted signal into a digital signal and outputs the digital signal as a digital current signal Id in accordance with the analog current signal I to the arithmetic operation section45.

The arithmetic operation section45is a processor configured to correct the sensor output signal PDd that is a position signal indicating the position of the magnet section36detected by the position detection section43using the correction information CI stored in the memory39and output the sensor output signal PDd. More specifically, the arithmetic operation section45corrects the sensor output signal PDd that is a position signal indicating the position of the magnet section36with the current value of the digital current signal Id detected by the current detection section44and the correction information CI.

The arithmetic operation section45is a circuit including a digital low pass filter45a, an amplification circuit45b, a digital low pass filter45c, and an addition circuit45d. Both the digital low pass filters45aand45chave predetermined cutoff frequencies.

The digital low pass filter45areceives the digital current signal Id and outputs the digital current signal Id at a predetermined low frequency to the amplification circuit45b.

The amplification circuit45bholds the correction information CI read from the memory39and outputs a correction signal Idc, which is a current signal obtained by correcting the digital current signal Id from the digital low pass filter45awith the correction information CI, to the addition circuit45d.

The correction information CI is information related to the amount of noise components due to a leaking magnetic flux from the voice coil motor32.

Noise components included in the outputted signal of the Hall device37are proportional to the magnitude of the drive current DI supplied to the coil section101. Therefore, the correction information CI here is a proportionality coefficient α.

The amplification circuit45boutputs a correction signal Idc that is proportional to the noise components due to the leaking magnetic flux from the coil section101by multiplying the current value of the digital current signal Id by the proportionality coefficient α.

Note that although the correction information CI here is the proportionality coefficient α, the correction information CI may be table data configured to store the correction signal Idc corresponding to the noise components in accordance with the value of the inputted digital current signal Id. In the case, the amplification circuit45breads and holds the table data from the memory39, outputs a correction amount corresponding to the current value of the inputted digital current signal Id based on the table data, and outputs the correction signal Idc corresponding to the value of the inputted digital current signal Id.

The digital low pass filter45creceives the sensor output signal PDd and outputs a signal at a predetermined low frequency to the addition circuit45d.

The sensor output signal PDd and the correction signal Idc are inputted to the addition circuit45d, and the addition circuit45doutputs a signal of a difference of the correction signal Idc indicating the noise components from the sensor output signal PDd as lens position information PI to the drive control section42.

In other words, the arithmetic operation section45calculates a correction amount by multiplying the current value of the digital current signal Id by the proportionality coefficient α, corrects the sensor output signal PDd by adding or subtracting the correction amount to or from the sensor output signal PDd that is a position signal, and outputs the sensor output signal PDd as lens position information PI to the drive control section42.

Note that the arithmetic operation section45may be configured of a processor including a central processing unit (CPU), a ROM, and a RAM and may perform all or a part of the aforementioned arithmetic operations by a program stored in the ROM.

The drive control section42controls a current or a voltage at the coil section101based on the lens position information PI that is an arithmetic operation result of the arithmetic operation section45.

Note that it is necessary to cause the amount of delay and the amount of attenuation of the current signal I at the timing of subtraction of the addition circuit45dto coincide with the amount of delay and the amount of attenuation of the sensor output signal PD from the sensor section33in order to accurately correct the position of the lens35a. Therefore, the cutoff frequency of the analog low pass filter44aand the cutoff frequency of the digital low pass filter45ccoincide with each other, and the cutoff frequency of the analog low pass filter43dand the cutoff frequency of the digital low pass filter45acoincide with each other.

As described above, the arithmetic operation section45outputs the lens position information PI, from which the noise components due to the leaking magnetic flux of the coil section101of the voice coil motor32have been removed, to the drive control section42. Therefore, since the drive control section42outputs, to the voice coil motor driver41, the driving command signal DS for causing the lens35ato move to the focusing position designated through a command using the focusing position command signal FC from the focal point control section46, it is possible to precisely control the position of the movable section53.

Therefore, according to the aforementioned embodiment, it is possible to provide an endoscope apparatus capable of removing influences of a leaking magnetic field from the coil and highly precisely controlling the position of the movable section when the movable section is driven to move forward and backward using the voice coil motor.

Note that although the example of the control of the position of the lens35afor focusing control has been described as the movable section in the aforementioned embodiment, the aforementioned embodiment can also be applied to control of a position of a lens for zooming control as the movable section.

As illustrated inFIG.1, for example, a zooming operation device25configured to drive a zooming lens, which will be described later, is provided along with various operation devices such as a release button at the operation section12. A button25aconfigured to perform zooming on a telephoto side and a button25bconfigured to perform zooming on a wide side of a zooming mechanism are provided in the zooming operation device25. If the user presses the button25a, the zooming operation device25outputs a signal to cause the zooming lens to move to perform zooming on the telephoto side while the button25ais being pressed, and the zooming lens is then stopped at a zooming position at the point when the pressing of the button25ais released.

Similarly, if the user presses the button25b, the zooming operation device25outputs a signal to cause the zooming lens to move to perform zooming on the wide side while the button25bis being pressed, and the zooming lens is then stopped at a zooming position at the point when the pressing of the button25bis released. Therefore, the user can observe the object at a desired zooming position or with a desired amount of zooming through the pressing operations on the buttons25aand25b.

Note that although the zooming operation device25is shown as the two buttons25aand25bprovided at the operation section12of the endoscope2here, the zooming operation device25may be another operation device such as a foot switch connected to the video processor3.

The user can cause the monitor4to display an endoscope image at an image angle that the user desires through an operation on the zooming operation device25. The video processor3drives an actuator of the endoscope2in response to the operation performed by the user on the zooming operation device25.

The zooming lens is fixed to the movable section53of the voice coil motor32, and the sensor section33outputs the sensor output signal PDa indicating the position of the magnet section36.

If the user presses the aforementioned button25aor25b, a zooming command signal ZC is outputted from the zooming operation device25as represented by the two-dotted dashed line inFIG.2. The drive control section42outputs the driving command signal DS for driving the voice coil motor32based on the zooming command signal ZC from the zooming operation device25and the lens position information PI from the arithmetic operation section45and causes the zooming lens to move. The zooming position of the image pickup optical system35changes with the movement of the zooming lens, and as a result, the size of the object image displayed on the monitor4changes.

Therefore, the aforementioned embodiment can also be applied to control of the position of the lens for zooming control using the voice coil motor based on the focal point position signal.

Further, although the correction information CI is stored in the memory39provided in the endoscope2and the video processor3corrects the position signal using the correction information CI read from the memory39of the endoscope2in the aforementioned embodiment, the video processor3may have a memory (not illustrated) that stores the correction information CI.

For example, information such as a manufacturing number of the endoscope2is stored as individual information in the memory39of the endoscope2, and correction information CI associated with the information such as the manufacturing number is stored in the memory of the video processor3. Therefore, even if the endoscope2does not have the correction information, the arithmetic operation section45can correct the position signal using the correction information read from the memory of the video processor3based on the information such as the manufacturing number.

According to the aforementioned embodiment, it is possible to provide an endoscope apparatus capable of removing influences of a leaking magnetic field from the coil and highly precisely controlling the position of the movable section when the movable section is driven to move forward and backward using the voice coil motor as described above.

The invention is not limited to the aforementioned embodiment, and various modifications, changes, and the like can be made without changing the gist of the invention.