JP4464858B2 - Electronic endoscope - Google Patents

Description

  The present invention relates to an electronic endoscope that includes a solid-state imaging device and can be used with various treatment tools.

As is well known, an endoscope can observe a living body or the like that cannot be directly seen, and is widely used for diagnosis and treatment mainly in the medical field. Electronic endoscopes that convert a subject image into an electrical signal by a solid-state imaging device such as a CCD and that can be observed on a monitor have become widespread. In recent years, electronic endoscopes employing a zoom optical system and high-resolution endoscopes using a multi-pixel solid-state image sensor have become widespread in order to observe a subject in detail.
The electronic endoscope that employs the former zoom optical system cannot adopt a complicated configuration due to the limitation of not increasing the size of the tip portion, and a variable magnification zoom optical system that moves one lens group and changes the viewing angle Is common.

Further, in a variable magnification zoom optical system as disclosed in Japanese Patent Application Laid-Open No. 2000-330019, as shown in FIG. 1 of this publication, the first lens group 10 having negative refractive power in order from the object side, and brightness The zoom lens includes a stop S, a second lens group 20 having a positive refractive power, and a third lens group 30 having a negative refractive power, and the first lens group 10 and the third lens group 30 do not move during zooming. The second lens group 20 moves to two different points on the optical axis that do not change the distance between the object images. G represents a filter.
According to this, it is possible to obtain a small and high performance two-focus type endoscope objective variable magnification optical system in which the distance between object images does not change at the time of zooming, and it is possible to perform detailed observation of a subject using a zoom optical system. There is.
Further, in the latter high-resolution endoscope using a multi-pixel solid-state image sensor, the subject can be imaged with higher resolution by using a multi-pixel solid-state image sensor than in the past. There is an effect that it becomes possible to observe in detail.
JP 2000-330019 A

In an endoscope using a variable magnification zoom optical system as disclosed in JP-A-2000-330019, the angle of view is changed by moving a lens in the imaging optical system when performing detailed observation of a subject. In order to change the magnification, in order to increase the magnification, it is necessary to narrow the angle of view.
On the other hand, in order for the treatment tool protruding from the channel tip opening to be imaged by the imaging optical system including the solid-state imaging device, the imaging is determined by the angle of view of the imaging optical system and the distance between the imaging optical system and the treatment instrument. The closer the optical system and the treatment instrument are, and the wider the angle of view of the imaging optical system, the faster the treatment instrument is imaged by the imaging optical system.

  When the subject is close to observe the subject in detail and the magnification is further increased, in the conventional example, the treatment tool projected from the opening at the end of the channel is not imaged within the field of view by the imaging optical system, and the subject is observed in detail. There is a problem that work such as treatment with a treatment tool becomes difficult. In other words, in the conventional example, when the object is set to the near point side (near view) for observing the subject in detail and the magnification of the zooming zoom optical system is increased, the angle of view becomes narrower and the treatment protrudes from the channel tip opening. There was a problem that the tool could not be captured within the field of view.

(Object of invention)
The present invention has been made in view of the above points, and in the case where an objective optical system having a variable focal length is used, an electronic internal device capable of being treated with a treatment tool while performing detailed observation of a subject on the near point side. An object is to provide an endoscope and an electronic endoscope system.

An electronic endoscope according to the present invention includes a solid-state imaging device having a predetermined number of pixels,
An objective optical system having a predetermined viewing angle to form an image on the solid-state imaging device;
Based on a luminance signal generated from an image signal obtained when an object with white and black bands of the same width is imaged, the maximum value of the luminance signal for the white object is Imax, and the luminance signal of the black object is Imin the minimum value, when the contrast I was defined as I = (Imax-Imin) / (Imax + Imin), a predetermined value of an object disposed from the tip of the interpolation join the club at a predetermined distance spaced positions near point side of the objective optical system In order to capture with the above contrast I, the focal length variable means for driving at least a part of the lenses constituting the objective optical system and changing the focal length of the objective optical system so that the depth of field partially overlaps. When,
And the treatment instrument insertion channel that can be inserted through the treatment置具,
Have
The focal length varying means has a depth of field at which the objective optical system can capture an object having a black and white pair band pitch of 35 μm on the near point side with the contrast I of approximately 10% or more, and There is a depth of field that can be captured with the contrast I of approximately 10% or more when a subject in a black and white pair band of 0.5 mm pitch is imaged at a position where the distance from the distal end of the insertion portion is 50 mm on the far point side. And
The treatment instrument insertion channel has a distal end opening so that the distal end of the treatment instrument protruded by a predetermined distance falls within the predetermined viewing angle by the objective optical system when set to the near point side by the focal length changing means. Provided,
Under the condition that the subject of the band of the black and white pair with the 35 μm pitch can be identified with the resolving power that the contrast I is 10% or more, the black and white pair with the 35 μm pitch and the tip of the tip lens surface of the objective optical system Let d be the distance from the subject in
The ray height Lh at the distal lens surface of the objective optical system, the radius R of the distal opening of the treatment instrument insertion channel, the distance D between the optical axis of the objective optical system and the center of the distal opening, and the objective optical system When the angle of view θ that can be imaged on the solid-state imaging device,
D ≦ d / tan (90 ° −θ / 2) + Lh−R
It is characterized by satisfying .
With the above configuration, when an objective optical system with a variable focal length is used, treatment with a treatment instrument is possible while observing the subject in detail on the near point side.

The present invention also provides a channel through which the treatment tool is inserted, an objective optical system that connects an optical image of a subject, and a light receiving surface disposed at a position where the objective optical system forms an image, and the optical image formed on the light receiving surface. An electronic endoscope having a solid-state imaging device for photoelectrically converting an image in an insertion portion; an image processing device for converting an image signal from the solid-state imaging device into a video signal for display on a monitor;
In an electronic endoscope system equipped with
The luminance signal obtained when the white subject is imaged based on the luminance signal that is provided in the electronic endoscope and is generated from the video signal obtained when the white and black belt subjects having the same width are imaged. placing the maximum value Imax, Imin the minimum value of the luminance signal to the black object, the contrast I when defined as I = (Imax-Imin) / (Imax + Imin), a position spaced a predetermined distance from the tip of the interpolation join the club A focal length variable means for changing the focal length of the objective optical system in order to capture the subject at a near point side of the objective optical system with a predetermined contrast I or more,
A treatment instrument insertion channel provided in the electronic endoscope and capable of inserting a treatment instrument;
Have
The focal length varying means has a depth of field at which the objective optical system can capture an object having a black and white pair band pitch of 35 μm on the near point side with the contrast I of approximately 10% or more, and There is a depth of field that can be captured with the contrast I of approximately 10% or more when a subject in a black and white pair band of 0.5 mm pitch is imaged at a position where the distance from the distal end of the insertion portion is 50 mm on the far point side. And
The treatment instrument insertion channel has a distal end opening so that the distal end of the treatment instrument protruded by a predetermined distance falls within the predetermined viewing angle by the objective optical system when set to the near point side by the focal length changing means. Provided,
Under the condition that the subject of the band of the black and white pair with the 35 μm pitch can be identified with the resolving power that the contrast I is 10% or more, the black and white pair with the 35 μm pitch and the tip of the tip lens surface of the objective optical system Let d be the distance from the subject in
The ray height Lh at the distal lens surface of the objective optical system, the radius R of the distal opening of the treatment instrument insertion channel, the distance D between the optical axis of the objective optical system and the center of the distal opening, and the objective optical system When the angle of view θ that can be imaged on the solid-state imaging device,
D ≦ d / tan (90 ° −θ / 2) + Lh−R
It is characterized by satisfying .
With the above configuration, when an objective optical system with a variable focal length is used, treatment with a treatment instrument is possible while observing the subject in detail on the near point side.

  According to the present invention, there is provided an electronic endoscope and an electronic endoscope system capable of performing treatment with a treatment tool while performing detailed observation of a subject on the near point side when an objective optical system having a variable focal length is used. realizable.

  Embodiments of the present invention will be described below with reference to the drawings.

1 to 8 relate to a first embodiment of the present invention, FIG. 1 is a configuration diagram showing a schematic configuration of an electronic endoscope system including the first embodiment of the present invention, FIG. 2 is a sectional view of an imaging unit, FIG. 3 is an explanatory view showing a state in which the imaging unit is set to the near view side and the far view side, FIG. 4 is a front view of the distal end surface of the insertion portion tip of the electronic endoscope of the present embodiment, and FIG. 6 is a schematic cross-sectional view taken along line AA in FIG. 4, FIG. 6 is a flowchart of the autofocus operation, and FIG. 7 is a cross-sectional view when the treatment instrument is inserted into the treatment instrument channel and the treatment instrument protrudes from the distal end opening. 8 is an explanatory view of the operation on the near point side of the present embodiment.
As shown in FIG. 1, the electronic endoscope system 1 is built in the electronic endoscope 2 of the first embodiment, a light source device 3 that supplies illumination light of the electronic endoscope 2, and the electronic endoscope 2. An image processing device (signal processing device) 4 that performs signal processing on the imaging means, and a high-definition TV (HDTV) that displays an endoscopic image when a standard video signal output from the image processing device 4 is input. (Abbreviation) It is comprised from the monitor 5 corresponding to a system.

The electronic endoscope 2 according to the present embodiment includes an elongated insertion portion 7 to be inserted into a subject and an operation portion that is provided at the rear end of the insertion portion 7 and is operated by an operator such as an operator. 8 and a cable portion 9 extending from the operation portion 8.
The insertion portion 7 is provided with a hard distal end portion 11 at the distal end, and an imaging unit and the like to be described later are provided at the distal end portion 11.
A light guide 14 for transmitting illumination light is inserted into the insertion portion 7, and the rear end side of the light guide 14 reaches the light guide connector 15 provided at the end portion via the cable portion 9. By connecting the light guide connector 15 to the light source device 3, illumination light is supplied from the light source device 3 to the rear end surface of the light guide 14.

Illumination light supplied from the light source device 3 is transmitted by the light guide 14, and the illumination lenses 16 a and 16 b attached to the illumination window from the distal end surface fixed to the distal end portion 11 so as to face the distal end surface (see FIG. 4). ) To illuminate a subject such as an affected part in a body cavity.
The distal end portion 11 is provided with an observation window (imaging window) adjacent to the illumination window. The imaging window has an objective lens system (objective optical system) 17 for connecting an optical image of the illuminated subject, and this An imaging unit 19 including, for example, a charge imaging element (abbreviated as CCD) 18 as a solid-state imaging element having a light receiving surface (photoelectric conversion surface) disposed at the imaging position of the objective lens system 17 is disposed.
One end of a signal cable 21 is connected to the imaging unit 19, and the signal cable 21 inserted into the insertion portion 7 is further inserted into the cable portion 9 and the other end is connected to the signal connector 22 at the rear end. .

By connecting this signal connector 22 to the image processing device 4, the CCD 18 is driven by the CCD drive signal from the CCD drive unit 23 of the image processing device 4, and the CCD 18 outputs a photoelectrically converted image signal (imaging signal). .
This imaging signal is signal-processed in the image processing device 4 to generate a video signal, and an endoscopic image is displayed on the monitor 5.
In addition, a channel 25 that allows various treatment tools to be inserted is provided in the insertion portion 7. The channel 25 includes a channel distal end opening (also referred to as a distal end opening or a forceps opening) 26 that opens at the distal end portion 11, a treatment instrument insertion port 27 near the front end of the operation unit 8, a distal end opening 26 and a treatment instrument insertion port 27 And a channel tube 25a for connecting the two.

Then, by inserting the treatment tool 28 from the treatment tool insertion port 27, the distal end side of the treatment tool 28 can be protruded from the distal end opening 26, and the affected tissue is collected or subjected to treatment such as excision. To be able to.
Further, in this embodiment, together with the subject to be inspected or treated such as the affected tissue, the distal end side of the treatment tool 28 protruding from the distal end opening 26 is placed in the field of view of the imaging unit 19 and this protruding treatment tool. 28 is displayed on the display surface of the monitor 5 so that treatment and the like can be performed smoothly.
In this embodiment, the CCD 18 is a mosaic color filter type CCD having a complementary mosaic color filter, has a pixel pitch of 2.5 μm, and has an effective number of pixels for monitor display of 1.3 million pixels. is doing.

The imaging unit 19 uses an objective lens system 17 constituted by a variable focus optical system in which the angle of view hardly changes when the focal position having a maximum angle of view of, for example, about 120 ° to 140 ° is changed. As shown in FIG. 2, the cemented lens 17 is moved back and forth on the optical axis O of the objective lens system 17 by the actuator 29, and from the near view (near point side) to the distant view (far point side) as shown in FIG. Can be imaged on the CCD 18 with high resolving power.
The objective lens system 17 has an Fno (F number) set to, for example, about 10.0 or less so as not to exceed the diffraction limit of light. In addition, the maximum resolving power is set when the object distance is close.
The configuration of the imaging unit 19 in the present embodiment will be described with reference to FIG.

A plurality of lenses (including optical elements) 17a, 17b, and 17c in the previous stage constituting the objective lens system 17 are fixed to the lens frame 31 with proper surface intervals and centering of the respective lenses.
In the case of FIG. 2, the spacing between the lenses 17 b and 17 c is set by the spacer 32. The first, second, and third lenses 17a that constitute the objective lens system 17 and are sequentially arranged from the front end side are a plano-concave lens, a biconvex lens, and an infrared cut filter, respectively.
In addition, a lens holding frame portion 34 a holding a cemented lens 17 d is provided in the CCD frame 33 fitted to the lens frame 31 so as to be slidable in the direction of the optical axis O of the objective lens system 17.
In the CCD frame 33, a parallel plate lens 17e and a CCD chip 18b are fixed at a position on the rear side of the lens holding frame portion 34a.

The CCD 18 is mounted on a sealing glass 18a, a CCD chip 18b whose light-receiving surface (imaging surface) is protected by the sealing glass 18a, a CCD substrate 18c connected to the CCD chip 18b, and the CCD substrate 18c. It is composed of a CCD driving part 18d.
A CCD substrate 18c is electrically connected to the CCD chip 18b by bump connection or the like. Also, a CCD driving component 18d such as a coupling capacitor and a current amplification transistor is soldered onto the CCD substrate 18c. A sealing glass 18a for protecting the light receiving surface is bonded and fixed to the light receiving surface of the CCD chip 18b with an optical adhesive or the like.
The lens frame 31 is fitted to the CCD frame 33 so as to be movable in the optical axis direction of the objective lens system 17, and the optical axis of the objective lens system 17 and the light receiving surface of the CCD chip 18b are perpendicular to each other. The CCD chip 18b is bonded and fixed to the CCD frame 33.

Further, in this embodiment, a lens holding frame portion which is disposed in the CCD frame 33 and has a positive power (refractive power), for example, is fitted to the inner peripheral surface of the CCD frame 33 and is movable. The lens holding frame portion 34a is connected to an actuator connecting portion 34c outside the CCD frame 33 through an arm portion 34b penetrating through a long groove 33a provided in the CCD frame 33.
The lens holding frame portion 34a, the arm portion 34b, and the actuator connecting portion 34c form a moving lens frame 34 that moves the cemented lens 17d.
An actuator 29 that moves the cemented lens 17d together with the moving lens frame 34 via the actuator connecting portion 34c includes an actuator moving portion 29a that is connected to the actuator connecting portion 34c, and the actuator moving portion 29a is connected to the objective lens system 17. The actuator body 29b moves in a direction parallel to the optical axis O. The actuator body 29 b is fixed on the outer peripheral side of the CCD frame 33.

The actuator main body 29b is connected to an actuator driving unit 36 (see FIG. 1) provided in the image processing apparatus 4 via a signal line 35, and the actuator main body 29b operates by an actuator driving signal from the actuator driving unit 36. .
The actuator main body 29b can move the actuator moving portion 29a to the rear side, which is the actuator main body 29b side, or to the front side away from the actuator main body 29b in accordance with the actuator drive signal. .
The actuator driving unit 36 generates (outputs) an actuator driving signal corresponding to a control signal from the CPU 37 c constituting the autofocus unit 37 provided in the image processing apparatus 4.

In the state shown in FIG. 2, the cemented lens 17d is in a state set near the center of the movable range (moving range), and in the setting state in the foreground that is moved to the most front side by the actuator drive signal, 3 is set at a position indicated by a two-dot chain line in this state, and in this state, a close-up scene focused on the near point side is imaged on the CCD chip 18b with a high resolution within a depth of field of 5.2 mm to 10 mm. .
Further, when the lens is moved to the rearmost side by the actuator drive signal, the cemented lens 17d is set to the rearmost position shown by the solid line in FIG. 3, and this state is a far-field setting state at the far point side. Become. In this distant view setting state, the distant view is focused, and the distant view is imaged on the CCD chip 18b with a predetermined resolution and a large depth of field of 10 to 100 mm.
In this way, the cemented lens 17d can be set to move to an arbitrary position within the movable range, with the range from the near view position to the far view position as a movable range. Since FIG. 3 is a diagram for explaining the operation, only some of the components are denoted by reference numerals.

As shown in FIG. 2, the CCD substrate 18c is provided with lands (not shown) for soldering the signal lines of the signal cable 21, and the signal lines of the signal cable 21 are soldered. A CCD protective frame 38 for mechanical protection is disposed from the CCD frame 33 through the CCD chip 18b to the connection portion of the signal cable 21 with the CCD substrate 18c.
The CCD protective frame 38 is provided with a notch at a position near the back surface of the CCD chip 18b. For example, aluminum alloy or copper having good thermal conductivity so as to be inserted from the notch. A heat radiating member 39 made of an alloy is disposed. The heat radiating member 39 is mechanically connected to the heat radiating cable 40 using a metal having good thermal conductivity as a conductor by soldering or adhesive.
The inside of the CCD protective frame 38 is filled with sealing resin 41, and the periphery of the CCD chip 18b is sealed with a heat-shrinkable tube 42. The heat dissipation cable 40 is soldered to a member having a large heat capacity, for example, the distal end portion 11 of the insertion portion 7.

The signal cable 21 is obtained by further combining a plurality of coaxial lines and a plurality of single wires, and winding a tape made of fluororesin, on which a copper wire is wound as a collective shield, and further made of fluororesin Is wrapped with a Teflon (registered trademark) sheath.
As shown in FIG. 4, the distal end portion 11 of the insertion portion 7 includes an imaging unit 19 including an objective lens system 17 whose outer diameter of the first lens 17 a at the distal end is, for example, φ2.8 mm, a channel distal end opening 26, Illuminates the subject with light transmitted / guided by an air / water supply nozzle 43 that removes dirt adhering to the outer surface of the objective lens system 17 by supplying water or air, and a light guide device 14. Illumination lenses 16a and 16b are provided for this purpose.
The imaging unit 19 is attached to the distal end portion 11 so that the vertical direction on the monitor 5 when the subject is imaged and displayed on the monitor 5 coincides with the vertical direction of the distal end portion 11 of the insertion portion 7 shown in FIG. It has been. Further, the channel tube 25a in the present embodiment uses, for example, a tube having an inner diameter of 2.8 mm made of Teflon (registered trademark).

As shown in FIG. 5, the optical axis O of the objective lens system 17 and the tip opening 26 (to which the tip of the channel tube 25a is connected) are arranged in parallel. In this embodiment, the objective lens system 17 The distance D between the center (optical axis O) and the center axis of the tip opening 26 is set to 6 mm, for example. Twice the radius R of the tip opening 26 is 2.8 mm, which is the same as the inner diameter of the channel tube 25a.
As shown in FIG. 1, the light source device 3 includes a lamp 45, and the illumination light of the lamp 45 is adjusted in the amount of transmitted light by the opening of the diaphragm 47 driven by the diaphragm driving unit 46, and then the condenser lens 48. Then, the light guide connector 15 enters the incident end face of the light guide 14. As described above, illumination light is emitted from the tip of the light guide 14 to the subject side through the illumination lenses 16a and 16b.

The light guide 14 is branched into two in the insertion portion 7, and illumination light is emitted from the illumination lenses 16a and 16b disposed at two locations in the distal end portion 11 as shown in FIG.
As shown in FIG. 1, the image processing apparatus 4 includes a CDS circuit 49 to which an image signal from the CCD 18 is input. After the signal component is extracted by the CDS circuit 49, the image processing apparatus 4 is digitally converted by an A / D converter 50. Converted to a signal.
The digital image signal converted by the A / D converter 50 is input to a signal conversion unit 51 that generates a video signal composed of a luminance signal and a color signal. The video signal generated by the signal conversion unit 51 is input to an image processing unit 52 that performs various image processing such as γ correction. The output signal of the image processing unit 52 is input to the D / A converter 53, converted into a video signal corresponding to an analog HDTV system, and then output to the monitor 5.

Further, the luminance signal from the signal conversion unit 51 is input to an automatic light control unit 54 that generates an automatic light control signal, and the automatic light control unit 54 generates an automatic light control signal. The automatic light control unit 54 includes a treatment instrument detection unit 54a that detects a treatment instrument, a luminance detection unit 54b that detects an average level of the luminance signal input from the treatment instrument detection unit 54a, and a detected luminance signal. A light control signal generation unit 54c that compares the average level with a reference value serving as a reference and outputs a difference signal from the reference value as an automatic light control signal.
The treatment instrument detection unit 54a detects that the treatment instrument has entered the field of view of the imaging unit 19 based on, for example, the amount of reflected light or the color of the treatment instrument (in other words, the image of the treatment instrument is formed on the light receiving surface of the CCD 18). Is detected.
In addition, when the treatment instrument detection unit 54a detects the treatment instrument, the luminance detection unit 54b has a peak luminance (light amount) near the area where the image of the treatment instrument is formed, or an average luminance near this area. Detect (light intensity).

In addition, when the treatment instrument detection unit 54a does not detect a treatment instrument, the luminance detection unit 54b detects a peak luminance or an average luminance over the entire screen.
In addition, the dimming signal generation unit 54c generates an automatic dimming signal that adjusts the amount of illumination light of the light source device 3 so that an appropriate brightness signal can be obtained from the peak luminance and average luminance signals from the luminance detection unit 54b. And output to the aperture driving unit 46 of the light source device 3.
The automatic light control signal of the automatic light control unit 54 is input to the diaphragm drive unit 46 of the light source device 3, and the diaphragm drive unit 46 automatically adjusts the opening amount of the diaphragm 47 in accordance with the automatic light control signal, thereby adjusting the light control signal. Control is performed so that an image having brightness suitable for observation corresponding to the reference value of the generation unit 54c is obtained.
Further, the luminance signal of the signal detection unit 51 is input to the brightness detection unit 37a constituting the autofocus unit 37, and the brightness of the image is detected by the brightness detection unit 37a.

The output signal of the image processing unit 52 is input to a contrast detection unit 37b that constitutes the autofocus unit 37, and the contrast of the output signal is detected by the contrast detection unit 37b.
The brightness information detected by the brightness detection unit 37a and the contrast information detected by the contrast detection unit 37b are input to the CPU 37c. The CPU 37c uses the brightness information and the contrast information, for example, auto-focus control of a mountain climbing method. I do.

  In the electronic endoscope 2 of the present embodiment, a part of the cemented lens 17d in the objective lens system 17 is arranged so as to be movable in the direction of the optical axis O, and the range from the near view position to the distant view position is continuous. The variable focal length optical system is employed in which the focal length changes with little change in the angle of view in accordance with the movement.

Then, the cemented lens 17d is focus-controlled by the autofocus unit 37 so that it is always set to a focus state in a range from a foreground to a distant view so that an image can be taken with a high resolution and a predetermined depth of field. Yes.
Further, in this embodiment, as described below, even when set to a close-up view, a wide viewing angle (viewing angle) is ensured, and even when a treatment tool is used, the channel 25 protrudes from the distal end opening 26. The distal end side of the treatment tool is placed in the field of view so that detailed treatment can be easily performed.

Specifically, in this embodiment, when the distal end side of the treatment instrument 28 inserted into the channel 25 protrudes from the distal end opening 26, for example, a high resolution (resolution) capable of identifying black and white with a pitch of 35 μm can be obtained. At the object distance (subject distance) on the side, the distal end side of the treatment instrument 28 falls within the field of view of the imaging unit 19, in other words, an image on the distal end side of the treatment instrument 28 is formed on the light receiving surface of the CCD 18.
The operation of the present embodiment having such a configuration will be described below.
As shown in FIG. 1, the light guide connector 15 of the electronic endoscope 2 is connected to the light source device 3, and the signal connector 22 is connected to the image processing device 4. Further, the cable of the monitor 5 is connected to the video output terminal of the image processing apparatus 4 so that the endoscopic examination can be performed.

Then, a power switch (not shown) is turned on to supply illumination light from the light source device 3 to the light guide 14, and the illumination light is emitted from the illumination lenses 16 a and 16 b via the light guide 14 and imaged by the imaging unit 19. Make the subject ready for illumination. In addition, an image captured by the CCD 18 of the imaging unit 19 is displayed on the monitor 5 via the image processing device 4.
Next, the insertion portion 7 of the electronic endoscope 2 is inserted into the patient's body cavity, and the distal end portion 11 of the insertion portion 7 can observe the subject at the site where the endoscopic examination of the affected part or the like is performed in the body cavity. To. In this case, the objective lens system 17 in the imaging unit 19 provided at the tip 11 forms an image of the subject on the light receiving surface of the CCD 18. The image formed on the light receiving surface of the CCD 18 is photoelectrically converted into an image signal.

This image signal is input to the CDS circuit 49 of the image processing apparatus 4 via the signal cable 21 and the signal connector 22. This image signal has a waveform including reset noise other than the signal component, and becomes a baseband signal from which the signal component has been extracted by the CDS circuit 49. The output signal of the CDS circuit 49 is input to an A / D converter 50, and the A / D converter 50 converts an image signal that is an analog signal into a digital signal. The image signal converted into the digital signal is converted into a video signal by the signal converter 51.
In this case, since a complementary color mosaic color filter is employed as the CCD 18 in this embodiment, the signal conversion unit 51 is, for example, a luminance signal obtained by averaging the signal outputs of the pixels of four adjacent color filters, It is converted into a video signal such as a color difference signal obtained by the difference in pixel signal output of each color.

The video signal is subjected to contrast adjustment, color adjustment, display size adjustment, and the like appropriate for monitor display by the image processing unit 52.
Thereafter, the D / A converter 53 converts the video signal to an analog HDTV system that can be displayed on the monitor 5. The monitor 5 displays an image of the subject imaged by the CCD 18 corresponding to the input HDTV video signal on the monitor screen 5a.
First, the automatic light control function will be described.
When the treatment instrument 28 is not within the field of view of the imaging unit 19, the automatic light control unit 54 detects the brightness of the entire screen (specifically, peak luminance or average luminance) by the luminance detection unit 54b. It outputs to the light control signal generation part 54c. The dimming signal generation unit 54c outputs a control signal, specifically an automatic dimming signal, so that the light source device 3 is brightened when the screen is dark. Further, when the screen is too bright, an automatic dimming signal is output as a control signal for controlling the light source device 3 so that the light is dimmed.

With this automatic dimming signal, the diaphragm driving unit 46 in the light source device 3 drives the diaphragm 47 so that the illumination light amount incident on the rear end of the light guide 14 from the lamp 45 through the diaphragm 47 becomes an appropriate light amount. Adjust to.
Next, the function of automatic light control when the treatment tool 28 is used for collecting tissue for treatment or excising a lesioned part on a subject such as an affected part by endoscopic examination by the imaging unit 19 will be described. .
By inserting the treatment instrument 28 into the channel 25 and projecting the treatment instrument 28 from the distal end surface of the distal end portion 11 of the insertion portion 7 through the distal end face 26, the treatment instrument enters the field of view of the imaging unit 19. .
In this case, for example, from the color of the treatment instrument 28, the reflected light of the treatment instrument 28, etc., the treatment instrument detection unit 54a detects that the treatment instrument 28 has entered the field of view, and is constant around the treatment instrument 28. The brightness by the peak luminance and average luminance of the area is detected. The dimming signal generation unit 54c outputs an automatic dimming signal as a control signal so that the light source device 3 is dimmed if the brightness near the treatment instrument 28 is too bright, and the light source device 3 is dimmed if it is too dark. To do.

Then, the diaphragm driver 46 in the light source device 3 drives the diaphragm 47 by the automatic light control signal, and adjusts the amount of illumination light incident on the rear end of the light guide 14 from the lamp 45 through the diaphragm 47. With this automatic light control signal, it is possible to automatically perform light control so that the brightness in the vicinity of the region where the treatment instrument 28 falls within the field of view of the imaging unit 19 becomes a brightness suitable for observation.
Next, the operation of the heat radiating member 39 and the heat radiating cable 40 arranged in the imaging unit 19 will be described.
When the CCD 18 is driven, the CCD chip 18b and the CCD driving component 18d such as a current amplifier generate heat. In general, as the number of pixels increases, the drive frequency increases, the power consumption increases, and the CCD generates heat. Since the heat radiating member 39 is disposed adjacent to the CCD chip 18b and the CCD substrate 18c, the heat of the CCD chip 18b is conducted to the heat radiating member 39 and then conducted to the heat radiating cable 40.

Further, heat is transmitted to the distal end member of the insertion portion 7 to which the heat radiating cable 40 is connected, and the heat generated in the CCD chip 18b is dissipated to prevent extreme heat generation of the CCD chip 18b.
Further, since the signal cable 21 has a tape wound between the collective shield and the sheath, for example, when the signal cable 21 is subjected to twist mechanical stress, the difference between the twist of the sheath and the collective shield is different. Since the friction between the collective shield and the sheath due to the tension and the tensile force applied to the collective shield by the sheath are alleviated by the tape between the collective shield and the sheath, the torsion resistance is improved.
Further, in the present embodiment, the cemented lens 17d constituting the objective lens system 17 is controlled by the autofocus unit 37 so that the subject image is always focused on the light receiving surface of the CCD 18.

In this case, the brightness detection unit 37a of the autofocus unit 37 detects the average brightness of each frame from the luminance signal from the signal processing unit 51 and outputs it to the CPU 37c. The contrast detection unit 37b detects the contrast in each frame from the high-frequency luminance signal in the output signal of the image processing unit 52, and outputs the detected contrast to the CPU 37c.
The CPU 37c determines whether or not the brightness detected by the brightness detection unit 37a is equal to or greater than a predetermined value. If the brightness exceeds the predetermined value, the CPU 37c uses a high-frequency luminance signal detected from the contrast detection unit 37b. Based on the contrast information, the focus state is detected by the hill-climbing method, and the cemented lens 17d is set at the focus state position.
FIG. 6 shows the processing contents for the hill-climbing autofocus (abbreviated as AF in FIG. 6).

First, in the first step S1, the CPU 37c determines the lens moving direction. As shown in FIGS. 2 and 3, a determination process is performed to determine which direction is the hill-climbing direction (the direction in which the contrast increases) at the starting lens position when performing this hill-climbing autofocus.
Specifically, the CPU 37c controls the actuator driving unit 36 to move the cemented lens 17d to one side via the actuator 29, and at this time, whether the contrast information output from the contrast detecting unit 37b increases before and after the movement. Make a decision. Then, the CPU 37c determines that the direction in which the contrast increases is the lens moving direction, and moves the cemented lens 17d in that direction.

In the next step S2, the CPU 37c detects the peak value of the contrast when the cemented lens 17d is moved in the direction in which the contrast increases. After moving in the hill-climbing direction where the contrast increases and past the focus position (focus position), it becomes smaller than the peak value.
Therefore, the peak value can be detected by moving the cemented lens 17d to a position slightly past the peak value.
In the next step S3, the CPU 37c controls the actuator driving unit 36 so as to return the cemented lens 17d to a position corresponding to the peak value. In this way, the cemented lens 17d can be set at the focus position.

And it returns to step S1 and repeats the process of step S1-S3. In this way, the focus state can always be maintained, and even when the distance to the subject changes, the subject is imaged on the CCD 18 with a high resolution while maintaining a predetermined depth of field. The monitor 5 displays an image of the subject imaged on the CCD 18, that is, a high-resolution image that maintains a predetermined depth of field.
Next, a case where a treatment tool is inserted into the channel 25 for treatment will be described. The operator inserts the treatment instrument to be used into the treatment instrument insertion port 27 provided near the operation unit 8. The treatment instrument inserted from the treatment instrument insertion port 27 passes through the channel 25 of the channel tube 25 a in the insertion portion 7 and is guided to the distal end portion 11 side of the insertion portion 7. When the operator further inserts the treatment instrument 28 into the deep side, the distal end of the treatment instrument 28 protrudes from the channel distal end opening 26 of the distal end portion 11.

As shown in FIG. 7, the necessary condition for the protruding treatment tool 28 to be imaged by the imaging unit 19 is the minimum protrusion amount Hmin of the treatment tool 28 from the distal end surface of the distal end portion 11 of the insertion portion 7, as shown in FIG. When the treatment instrument 28 is most shifted to the imaging unit 19 side, the light beam height Lh = 1.2 mm at the tip lens surface of the imaging unit 19, the radius R = 1.4 mm of the tip opening 26, and the angle of view of the imaging unit 19. For example, θ is set to θ = 138 °, and the distance D = 6 mm between the optical axis O of the imaging unit 19 and the center of the tip opening 26 is derived as shown in the following Expression 1.
Hmin = (D−Lh−R) × tan (90 ° −θ / 2) = 1.38 mm (Formula 1)
On the other hand, when the treatment instrument 28 is positioned in the direction farthest from the imaging unit 19, the condition necessary for the treatment instrument 28 to protrude and the entire distal end of the treatment instrument 28 to be imaged by the imaging unit 19 is an insertion. The amount of protrusion Hall of the treatment instrument 28 from the distal end surface of the distal end portion 11 of the portion 7 is derived as shown in Expression 2.

Hall = (D−Lh + R) × tan (90 ° −θ / 2) = 2.45 mm (Formula 2)
As shown in Equations 1 and 2, the treatment instrument 28 starts to enter the field of view of the imaging unit 19 when the amount of protrusion from the distal end surface of the distal end portion 11 is 1.38 mm or more, and is projected 2.45 mm. Nearly the entire tip of the treatment instrument 28 falls within the field of view.
As described above, in the state set on the near point side of the imaging unit 19 in the present embodiment, the depth of field is 5.2 mm to 10 mm, and the distal end side of the treatment instrument 28 is surely within the field of view of the imaging unit 19. It becomes visible even on the monitor 5.
Next, with reference to FIG. 8, the operation when the imaging unit 19 images a subject or the like having a black and white pair band of 35 μm pitch in the state set to the near point side will be described.

In FIG. 8, the insertion portion 7 of the electronic endoscope 2 of the present embodiment is inserted into the body cavity, and the treatment unit 28 is imaged with the imaging unit 19 provided at the distal end portion 11 while the treatment target region side is imaged. The schematic in the case of making it protrude from the front-end | tip opening 26 and performing a treatment is shown.
In this case, as conditions for easy treatment, it is desirable that the affected part to be treated can be observed in detail, and the distal end side of the treatment instrument 28 protruding from the distal opening 26 can be observed in detail. desired.
In the present embodiment, these are satisfied as follows. First, in order to clarify the description, the luminance contrast G (MTF) is defined as follows.

When an object of white and black stripes having the same width is imaged on the light receiving surface of the CCD 18 by the objective lens system 17, the maximum luminance value of the white object is Gmax, and the black object is The minimum luminance value is defined as Gmin, and the luminance contrast G = (Gmax−Gmin) / (Gmax + Gmin) is defined.
When the luminance contrast G is defined in this way, the imaging unit 19 configured as described above has the black and white pair band 60 when the object distance is 5.2 mm to 6.8 mm in the state set to the near point. When an object having a pitch of 35 μm is imaged, the luminance contrast G between the white band and the black band formed on the CCD light receiving surface is 10% or more.
The image of the subject in a black and white pair band with a pitch of 35 μm formed on the light receiving surface of the CCD 18 by the objective lens system 17 is formed by an image signal output from a pixel on which a white band is formed and a black band. The difference between the image signals output from the pixels is about 10% or more.

The image signal is input to the image processing unit 52 via the CDS circuit 49, the A / D converter 50, and the signal conversion unit 51. For example, gamma processing suitable for the monitor 5, low-pass filter processing for removing noise, etc. Is given.
The maximum value of the luminance signal obtained from the white subject is Imax, the minimum value of the luminance signal obtained from the black subject is Imin, and the contrast I is I = (Imax−Imin) / (Imax + Imin). When defined, the output is performed so that the contrast I becomes 10% or more (when an object having a pitch of 35 μm in the black and white pair is imaged). As described above, the black and white pair band of 35 μm pitch imaged by the imaging unit 19 can be visually recognized on the monitor 5 as the black and white pair band. In this way, when the contrast I is 10% or more, observation can be performed in an easily distinguishable state.

In FIG. 8, when an object distance of 6.8 mm is set to d in the state set to the near point side, and a black and white pair band (stripes) 60 having a pitch of 35 μm is arranged at that position, photoelectric conversion is performed by the CCD 18. When the contrast I in the luminance signal forming the video signal output from the signal conversion unit 51 is 10% or more as described above, the black and white pair band 60 having a pitch of 35 μm can be visually recognized on the monitor 5.
FIG. 8 also shows a state in which the treatment instrument 28 protrudes from the distal end opening 26 of the channel, and after the distal end of the treatment instrument 28 enters the field of view of the imaging unit 19, the distal end of the treatment instrument 28 is further projected forward. Is in a state of an object distance d in which a black and white pair band 60 with a pitch of 35 μm can be visually recognized. In this state, since the object distance d is larger than Hall of Expression 2, from Expression 2, d ≧ (D−Lh + R) × tan (90 ° −θ / 2) (Expression 5) is satisfied. In addition, if Formula 5 is rewritten,
D ≦ d / tan (90 ° −θ / 2) + Lh−R
It becomes.

For this reason, according to the present embodiment, when an optical system having a variable focal length is used, a subject such as an affected part to be treated can be observed in high detail by the treatment tool 28 and protruded in the vicinity thereof. The state of the distal end of the treatment instrument 28 can also be observed in high detail, and treatment is easy. Even in this state, since it has a predetermined depth of field, it is possible to grasp a wide range of states around the part to be treated, and to perform the treatment smoothly.
This embodiment has the following effects.
In this embodiment, a variable focus optical system in which the angle of view hardly changes when the focal position is varied is used as the objective lens system 17 constituting the image pickup unit 19, and therefore, compared with a single focus optical system. Thus, an endoscopic image with high resolution can be obtained from the near view side to the far view side.

Further, the distal end side of the treatment instrument 28 protruding from the distal end opening 26 of the channel 25 can be visually recognized on the monitor 5 at a distance where the black and white pair band of 35 μm pitch imaged by the imaging unit 19 can be visually recognized on the monitor 5. Therefore, in an endoscope using a conventional zoom optical system, the operability due to the narrowing of the angle of view during magnified observation can be improved. For example, according to the present embodiment, it is possible to easily perform treatment with the treatment tool 28 while performing detailed observation of a subject such as a pit pattern of the large intestine.
Further, in the state set to the near point side, the distance that the band of the black and white pair with a pitch of 35 μm is visible on the monitor is 5.2 mm to 6.8 mm. At the object distance, the distal end side of the treatment instrument 28 can be put in the field of view, and the distance reaching the maximum resolving power can be reached by projecting further forward.

Therefore, in the present embodiment, the distal end side of the treatment instrument 28 can be sufficiently placed in the visual field at a distance within the depth of field in the state set to the near point side, and the operation of the treatment instrument 28 is compared. The effect that it becomes easy is also acquired.
Furthermore, even when set to the far side, it is possible to obtain a subject image with a predetermined resolution and a greater depth of field than in the near side.

In addition, since the autofocus control is performed so that the variable focus optical system constituting the objective lens system 17 is in a focused state, the operator does not need a complicated operation and has a high resolution from a distant view to a close view. An endoscopic image can be observed.
Further, when the treatment tool 28 is inserted and the tip of the treatment tool 28 is displayed on the monitor 5, the amount of light emitted from the light source device 3 is controlled so that the brightness near the treatment tool 28 is optimal, so that treatment is easy. Become.
In this embodiment, the pixel pitch of the CCD 18 is 2.5 μm, the number of effective pixels is 1.3 million pixels, the maximum field angle of the imaging unit 19 is 138 °, and the depth of field on the near point side is 5.2 mm to 10 mm. The distance between the optical axis O of the image pickup unit 19 and the center of the tip opening 26 is 6 mm, but is not limited to this.

  For example, when a subject with a black and white pair band 60 having a pitch of 35 μm is imaged, there is a difference between an output signal obtained from a pixel that images the white subject and an output signal obtained from a pixel that images the black subject. When the pixel pitch, the number of effective pixels, the maximum angle of view, the depth of field on the near point side, etc. are changed so as to be 10% or more, and the 35 μm subject is imaged, the output signal difference is 10%. Even if the maximum angle of view and the distance between the optical axis O of the imaging unit 19 and the center of the tip opening 26 are changed so that the treatment tool can be observed at the object distance described above, substantially the same effect can be obtained. .

  In the above description, the effective number of pixels of the CCD 18 is 1.3 million pixels. However, in the case of the mosaic color filter method, the same effect can be obtained even with about 1.5 million pixels. In this case, the highest resolution is obtained. The effect that the distance which can be made can be enlarged further is acquired. In this embodiment, the complementary color mosaic filter type color CCD is used for explanation. However, the present invention is not limited to this, and the electronic endoscope uses three primary colors such as switching light as illumination light, and sequentially. A method of capturing a subject image with a monochrome (monochrome) CCD in synchronization with the irradiated light of the three primary colors and colorizing it with an image processing device may be used. Similar effects can be obtained.

In the case of this method, an R signal, a G signal, and a B signal can be obtained as a CCD output signal having about 650,000 effective pixels, and a luminance signal can be output to the monitor 5 without being generated. In this case, the G signal with the highest luminance may be regarded as the luminance signal.
The angle of view is preferably an angle of view of 100 ° or more that is used in a general endoscope in consideration of surrounding observability, and a wider angle of view has an effect that the treatment instrument detection distance is shortened.
Further, the image processing apparatus 4 and the monitor 5 of the present embodiment have been described as being compatible with HDTV video signals, but are not limited thereto, and are compatible with high resolution monitors such as SVGA and XGA. The display method described above may be used.

Furthermore, in the imaging unit 19 of the present embodiment, heat dissipation to the distal end member of the insertion portion 7 is disclosed by the heat dissipation member 39 and the heat dissipation cable 40 as means for dissipating the heat of the CCD 18. A structure may be used in which the cable 40 is not provided and a portion having a good thermal conductivity of the tip member of the insertion portion 7 is brought close to a portion facing the heat radiating member, and heat is radiated through a sealing resin having a good thermal conductivity.
Further, a part of the signal cable 21 may be used as the heat radiating cable 40. For example, a dummy cable not used for driving may be provided in the signal cable 21, or an external shield for the purpose of electromagnetic shielding of the signal cable 21 may be used. Further, the same heat dissipation effect can be obtained by fixing the conductor portion of the heat dissipation cable 40 near the CCD chip 18b with a sealing resin having good conductivity without providing the heat dissipation member 35.
In addition, an output stage inside the CCD chip 18b is arranged on the CCD substrate 18c as an external amplifier, and the power consumption of the CCD chip 18b is distributed to components on the external substrate, thereby suppressing the heat generation of the CCD chip 18b. It is valid.

  Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 9 shows an overall configuration of an electronic endoscope system 1B including the second embodiment. This electronic endoscope system 1B has two stages (automatic) instead of the electronic endoscope 2B in which a part of the electronic endoscope 2 in FIG. 1 is different from the autofocus unit 37 in the video processor 4 in the first embodiment. It has a video processor 4B including a CPU 71 having a focus control function 71a. The light source unit 3 and the monitor 5 have the same configuration as that of the first embodiment.

  The basic configuration of the electronic endoscope 2B of the present embodiment is the same as that of the first embodiment. The number of effective pixels of the CCD and a part of the configuration of the objective lens system are different. The positional relationship is different. Hereinafter, the difference will be described with emphasis.

10 is a front view of the distal end surface of the distal end portion 11 of the insertion portion 7 in the electronic endoscope 2B of the present embodiment as viewed from the front, FIG. 11 is a sectional view taken along line BB in FIG. 10, and FIG. The monitor display image when 28 is protruded from the front-end | tip part 11 is shown.
An imaging unit 19B including the objective lens system 72 and the CCD 73 shown in FIG. 10 or 11 is employed at the distal end portion 11 of the electronic endoscope 2B in the present embodiment.
This CCD 73 employs a pixel pitch of 2.8 μm and an effective number of pixels for monitor display of 800,000 pixels.
Further, the imaging unit 19B has, for example, an objective lens system 72 of a variable magnification optical system having a maximum field angle of 160 ° in the state set to the near point side (near view). A meniscus lens is disposed as the first lens 72a.

As shown in FIG. 10, the distal end portion 11 of the insertion portion 7 includes an imaging unit 19B including an objective lens system 72 having an outer diameter of the first lens 72a of 2.8 mm and a meniscus shape, and a channel distal end opening 26B. An air supply / water supply nozzle 43 that removes dirt adhered to the tip surface of the objective lens system 72 by supplying water and air, and illumination for illuminating the subject with light that passes through a light guide (not shown) connected to the light source device 3 Lenses 16a and 16b are disposed.
The imaging unit 19B is attached to the distal end of the insertion section so that the vertical direction on the monitor 5 when the subject is captured and displayed on the monitor 5 coincides with the vertical direction of the distal end of the insertion section shown in FIG.
The treatment instrument channel 25 having an inner diameter of 2.8 mm is arranged in a diagonally lower left direction slightly shifted from the horizontal direction with respect to the imaging unit 19B, and as shown in FIG. Assuming that the left-right direction is the X axis, a straight line connecting the central axis of the treatment instrument channel 25 and the optical axis O of the imaging unit 19B forms an angle α with respect to the X axis.

As shown in FIG. 11, the optical axis O of the objective lens system 72 and the tip opening 26B are arranged in parallel. In this embodiment, the center (optical axis O) of the objective lens system 72 and the tip opening 26B are arranged. The distance D of the central axis is 6 mm.
Also in this embodiment, the first lens 72 a, the second lens 72 b and the third lens 72 c shown in FIG. 11 are attached to the first lens frame 31, and the inside of the CCD frame 33 fitted to the first lens frame 31. Similarly to the first embodiment, the cemented lens 17d is movably disposed by the lens holding frame, and the cemented lens 17d is moved in the optical axis O direction via the actuator 29.
In addition, the CPU 71 provided in the video processor 4B basically focuses the cemented lens 17d between the two positions of the foreground position and the foreground position instead of continuously performing the autofocus control in the first embodiment. Focus control is performed so as to be close to. That is, two-stage (pseudo by auto switching) focus control is performed.

In this case, the CPU 71 reads the ID information of the electronic endoscope 2B connected to the video processor 4B from the scope ID memory 74, and stores the optical characteristic information of the imaging unit 19B of the electronic endoscope 2B in the RAM 71c. This optical characteristic information is information on a typical contrast change characteristic or resolution when the object distance is changed when the cemented lens 17d is set at a near view position and when it is set at a distant view position. is there.
Then, when performing the two-stage focus control, the CPU 71 checks the temporal change in the contrast information when the cemented lens 17d is set at one of the actually set positions, and the optical stored in the RAM 71c. By referring to the characteristic information, it is determined whether a larger contrast value is obtained when the change is switched to the other position, that is, whether or not the focus state is closer.

When the CPU 71 determines that a larger contrast value can be obtained by switching to the other position, the CPU 71 controls the actuator driving unit 36 to set the cemented lens 17d to the other position.
Further, even when the cemented lens 17d is set to the other position, the CPU 71 monitors the contrast information in that state in terms of time and performs the same operation, so that the two lens positions are more focused. The lens position is controlled to be close to.
In this case, the CPU 71 detects the brightness information from the luminance signal from the signal conversion unit 51 and further detects the contrast information from the image processing unit 52, and in the state of the predetermined brightness or higher, the contrast information as described above. The temporal change is monitored, and it is determined whether or not to switch by referring to the optical characteristic information, and the cemented lens 17d is controlled at two positions according to the determination result.

In this embodiment, when switching between two positions, a near view and a distant view, the objective lens system 72 in both states exhibits different optical characteristics. For example, it has the highest resolution in the foreground and, conversely, the resolution in the distance is slightly lower than that in the foreground, but has a greater depth of field than the foreground. Specifically, when the cemented lens 17d is set to the foreground side, the depth of field is changed from 4.4 mm to 12 mm, and when the cemented lens 17d is set to the far side, the depth of field is changed from 9 mm to 100 mm. The F number is adjusted so that
The resolution in both characteristics has a crossing (overlapping) part in a state of showing an almost opposite tendency at an intermediate distance between the foreground and the distant view, so that the crossing part is slightly deviated from the crossing position. Then, it can be determined to which position the cemented lens 17d is set is closer to the focus state (in-focus state). The CPU 71 performs the determination, and controls the position switching of the cemented lens 17d according to the determination result. In the present embodiment, the depth of field in the objective lens system 72 in the state set to the near view and the distant view is set so as to be continuous (overlapped) in a portion of a predetermined value or more, and a space having a predetermined value. In the range up to the frequency, the contrast I is also set to overlap in a portion having a predetermined value or more (for example, 10%) or more.

Next, the operation in the foreground in the present embodiment will be described.
First, the operation when the imaging unit 19B captures an image of a subject having a black and white pair band of 35 μm pitch in the foreground will be described.
In this imaging unit 19B, when an object distance of 4.4 mm to 5.8 mm and an object with a black-and-white pair band pitch of 35 μm is imaged in a state set at a near point, an image is formed on the CCD light receiving surface. The contrast G between the white band and the black band is 10% or more.
An image of a subject in a black and white pair band having a pitch of 35 μm formed on the light receiving surface of the CCD 73 by the objective lens system 72 is photoelectrically converted. The difference between the image signal output from the pixel on which the white band is formed and the image signal output from the pixel on which the black band is formed is approximately 11.5%.

The image signal is input to the image processing unit 52 via the CDS circuit 49, the A / D converter 50, and the signal conversion unit 51, and subjected to, for example, gamma processing suitable for a monitor, electrical mask processing, and the like. Then, the contrast I between the white band and the black band is output to the monitor 5 so that the contrast I becomes 10% or more. When the contrast I is 10% or more for the subject as described above, the white band and the black band can be distinguished from the displayed image, and observation can be performed with sufficient resolution. Thus, according to the present embodiment, the band of the black and white pair with a pitch of 35 μm picked up by the image pickup unit 19B can be visually recognized as the band of the black and white pair on the monitor.
Further, since the contrast value decreases as the object distance increases from the near view, the CPU 71 performs control to switch the cemented lens 17d to the far view position when it is determined that a greater contrast value can be obtained by switching. Do.

  By performing the switching control in this way, when the observation state is changed from the near view to the distant view, an endoscopic image can be obtained with the lens positions closer to the focus state at the two positions.

  The electrical masking process creates an octagonal display area 5b having an aspect ratio of 1: 1.2 in the display screen of the monitor 5 as shown in FIG. The subject imaged by the imaging unit 19B is displayed.

In the case of a horizontally long display area as shown in FIG. 12, the angle of view on the display area 5b obtained by the electrical masking process is the angle of view (θmax) having the largest point P in the diagonal direction. Mask processing is performed so that the field angle 160 ° of the objective lens system 72 coincides with the maximum field angle θmax. On the other hand, by the mask process, the angle of view becomes the narrowest on the monitor screen in the vertical direction, and then the angle of view in the horizontal direction becomes narrower.
The maximum diagonal point P is set so that the angle formed between the straight line connecting the point P and the center of the screen and the horizontal direction on the monitor screen is α, and the imaging unit 19B 10, since the X-axis direction of the distal end portion 11 of the insertion portion and the monitor horizontal direction coincide with each other, the treatment instrument channel 25 disposed at an angle α with respect to the X-axis. As shown in FIG. 12, the treatment tool 28 protruding from the distal end opening 26B is displayed from the vicinity of the P point in the lower left, which is roughly in the horizontal direction on the monitor 5, more strictly speaking, slightly below the horizontal direction. It is displayed in the area 5b.

In the present embodiment, a condition necessary for the treatment tool 28 protruding from the distal end opening 26B of the distal end portion 11 of the insertion portion to be imaged by the imaging unit 19B is the condition of the treatment tool 28 from the distal end surface of the distal end portion 11. When the treatment tool 28 is most shifted to the imaging unit 19B side as the minimum protrusion amount Hmin, the light ray height Lh = 1.31 mm at the tip lens surface of the imaging unit 19B, and the radius R = 2.8 mm of the tip opening 26B. The angle of view θ of the imaging unit 19B = 160 ° and the distance D = 6 mm between the optical axis O of the imaging unit 19B and the channel 25 are derived as shown in Expression 3.
Hmin = (D−Lh−R) × tan (90 ° −θ / 2) = 0.58 mm (Formula 3)
On the other hand, when the treatment tool 28 is positioned in the direction farthest from the imaging unit 19B, the conditions necessary for the treatment tool 28 to protrude and the entire distal end of the treatment tool 28 to be imaged by the imaging unit 19B are: As the amount of protrusion Hall of the treatment instrument 28 from the distal end surface of the distal end portion 11, it is derived as shown in Expression 4.

Hall = (D−Lh + R) × tan (90 ° −θ / 2) = 1.07 mm (Formula 4)
As shown in Equations 3 and 4, the treatment instrument 28 starts to enter the field of view of the imaging unit 19B when the amount of protrusion from the distal end surface of the distal end portion 11 is 0.58 mm or more and protrudes from 1.07 mm. The almost entire tip of the treatment instrument 28 falls within the visual field.
From the above, at a distance of 4.4 mm to 5.8 mm where a band of a black and white pair with a pitch of 35 μm set on the near point side of the imaging unit 19B in this embodiment is visible on the monitor, the distal end side of the treatment instrument 28 Enters the field of view of the imaging unit 19B and is visible on the monitor 5 as well.
This embodiment has the following effects.
Since the present embodiment employs a variable focus optical system whose focal length changes as the objective optical system constituting the imaging unit 19B, an image having a higher resolution from the near view side to the far view side than in the case of a single focus optical system. Can be obtained.
Here, in the present embodiment, the pixel depth of the CCD 73 is 2.8 μm, the number of effective pixels is 800,000 pixels, the maximum field angle of the imaging unit 19B is set to 160 °, and the depth of field is set to the near point side. The distance between the optical axis O of the imaging unit 19 </ b> B and the center of the tip opening 26 is 6 mm. However, the present invention is not limited to this.
For example, when a subject with a black and white pair band pitch of 35 μm is imaged, the difference between the output signal obtained from the pixel that images the white subject and the output signal obtained from the pixel that images the black subject is 10 If the pixel pitch, the number of effective pixels, the maximum angle of view, the depth of field on the near point side, etc. are changed so as to be more than 10%, and the 35 μm subject is imaged, the difference in output signal is 10% or more Even if the maximum angle of view and the distance between the optical axis O of the imaging unit 19 and the center of the distal end opening 26 are changed so that the treatment tool can be observed at the object distance as shown in FIG.

In this embodiment, the number of effective pixels is set to 800,000 pixels. However, in the case of the mosaic color filter method, the same effect can be obtained even with about 600,000 pixels. In this case, the depth of field on the near point side is reduced. Further, since the cross area of the depth with the depth of field on the far point side is widened, the effect that the focus can be switched more smoothly is obtained.
Also in this embodiment, three primary colors such as a switching type are used as illumination light, and a subject is captured by a monochrome (monochrome) CCD in synchronization with the sequentially irradiated light of the three primary colors and is colored by the image processing apparatus. In this case, when a CCD having about 250,000 effective pixels is used, an effect equivalent to that of the 600,000 pixels of the mosaic filter method can be obtained.

In this embodiment, as shown in FIG. 12, the display area 5b of the monitor screen 5a is a horizontally long octagon whose display size in the horizontal direction is longer than that in the vertical direction (vertical direction). It is not limited.
Further, more generally, by disposing the tip opening so as to correspond to the direction in which the display area in the display area is wide (or large), the treatment tool 28 protruding from the tip opening displays in the direction in which the display area is wide. You may be made to do.
As a first modification of the present embodiment, the two-stage autofocus control function 71a and the three-stage autofocus control function 71b may be selected by the mode switch SW1 by the CPU 71 as shown in FIG.

In the electronic endoscope system 1C shown in FIG. 13, for example, in the electronic endoscope system 1B shown in FIG. 9, the CPU 71 has a three-stage autofocus control function 71b in addition to the two-stage autofocus control function 71a.
The CPU 71 performs focus control in the two-stage autofocus mode or the three-stage autofocus mode according to a selection signal selected by, for example, the mode selector switch SW1 provided in the operation unit 8 of the electronic endoscope 2B.
Also in this modification, the scope ID memory 74 stores optical characteristic information unique to the electronic endoscope 2B. In this case, information on optical characteristics relating to contrast when the cemented lens 17d is set to an intermediate point set between the near point and the far point in addition to the near point and the far point is stored. Information for driving (moving) the cemented lens 17d is also stored at the position of the intermediate point.

Then, the CPU 71 of the video processor 4B reads out the optical characteristic information and stores it in, for example, the RAM 71c, and performs the two-stage focus control or the three-stage focus control in the second embodiment.
As a merit of performing the three-stage focus control, in the two-stage focus control of the near point and the far point, a valley between the optical characteristics of both of them is obtained near the intermediate position between them. It tends to be difficult to improve to have favorable characteristics.
For example, in the case of a near view and a distant view, when the depth of field is continuous at a predetermined value or more and the contrast I is 10% or more, the position can be switched to the middle point between the two. It is possible to continue with a greater depth of field value and a contrast I value than these conditions, and more improved optical characteristics can be realized.

In this way, by adopting a configuration in which the cemented lens 17d can be set also at the position of the intermediate point between the near point and the far point, the depth of field and the resolution can be increased, and thus more preferable optical characteristics can be realized. Is easy to do.
The control method for performing the three-stage focus control is similar to the two-stage. For example, in a state where the near point is set, the CPU 71 monitors temporal changes in contrast information in that state, and in this case, determines whether or not to switch between the near point state and the intermediate point.
Even in the state set to the middle point, the temporal change in contrast information is monitored, and depending on whether it is changing to the near point side or the far point side, Determine whether to switch. For this reason, it is possible to perform three-stage focus control with the same control as in the second embodiment.

FIG. 14 shows a CPU 71 portion in the second modification. As shown in FIG. 14, for example, the CPU 71 may perform a two-stage autofocus control function 71a and a two-stage manual control function 71d in accordance with the mode switching instruction signal of the mode switch SW1.
The two-stage autofocus control function 71a is the same as that described in the second embodiment. When the two-step manual control mode is set by the mode switch SW1, the CPU 71 moves the cemented lens 17d to the near point side when the near point instruction switch in the manual operation switch SW2 is operated.
On the other hand, when the far point instruction switch in the manual operation switch SW2 is operated, the CPU 71 performs a control operation of moving the cemented lens 17d to the far point side.
By providing the mode selection means in this way, the operator has a wider range of options for observation (imaging) when making a diagnosis or the like using the electronic endoscope 2B, and can realize a user-friendly one.

In FIG. 14, the two-stage autofocus control function 71a and the two-stage manual control function 71d have been described. However, in addition to this, the three-stage autofocus control function 71b and the three-stage manual control function are performed. Also good. Further, by using a CPU or the like, an autofocus control function in a plurality of stages and a manual control function in a plurality of stages may be performed. Further, using a CPU or the like, continuous autofocus control, multiple-stage focus control, and continuous or multiple-stage manual control may be performed according to the mode switching instruction operation.
Further, the image processing apparatus 4 and the monitor 5 of the present embodiment have been described as being compatible with HDTV video signals. However, the present invention is not limited to this. For example, video signals such as NTSC and PAL are used. It may be compatible. Further, a VGA type or SVGA type may be used.
Note that embodiments configured by partially modifying or combining the above-described embodiments and the like also belong to the present invention.

[Appendix]
1. A solid-state imaging device having a predetermined number of pixels;
An objective optical system having a predetermined viewing angle to form an image on the solid-state imaging device;
Based on a luminance signal generated from an image signal obtained when an object with white and black bands of the same width is imaged, the maximum value of the luminance signal for the white object is Imax, and the luminance signal of the black object is When the minimum value is defined as Imin and the contrast I is defined as I = (Imax−Imin) / (Imax + Imin),
In order to capture a subject with a pitch of 35 μm of a black and white pair band arranged at a predetermined distance from the distal end of the insertion portion with a contrast I of approximately 10% or more on the near point side of the objective optical system, the objective optical system is A focal position variable means for driving at least a part of the lenses to change the focal length of the objective optical system so that the depth of field partially overlaps;
A treatment instrument insertion channel opened so that the distal end of the treatment instrument protruded by a predetermined distance is disposed within the viewing angle when set to the near point side by the focal length varying means;
An electronic endoscope comprising:

2. An objective optical system that links the optical image of the subject;
A light receiving surface is disposed at a position where the objective optical system forms an image, and an electronic endoscope having a solid-state image sensor that photoelectrically converts an optical image formed on the light-receiving surface in an insertion portion; and An image processing device for converting the image signal of the image signal into a video signal for display on a monitor;
In an electronic endoscope system equipped with
Based on a luminance signal generated from a video signal obtained when imaging a white and black belt subject having the same width, the maximum value of the luminance signal obtained when imaging the white subject is Imax, and the black subject is When the minimum value of the luminance signal for I is defined as Imin and the contrast I is defined as I = (Imax−Imin) / (Imax + Imin),
In order to capture an object with a pitch of 35 μm of a black and white pair band arranged at a predetermined distance from the distal end of the insertion portion with a contrast I of approximately 10% or more on the near point side of the objective optical system, A focal length variable means for changing the focal length;
A treatment instrument insertion channel opened so that the distal end of the treatment instrument protruded by a predetermined distance is disposed within the visual field range on the monitor when set to the near point side by the focal length varying means;
An electronic endoscope system comprising:

  The insertion part is inserted into the body cavity, and the subject such as the affected part can be imaged in a state where it can be observed with high definition on the near view side. Therefore, it is suitable for smoothly performing treatment for treatment by projecting the distal end side of the treatment tool inserted into the channel from the distal end opening of the channel.

BRIEF DESCRIPTION OF THE DRAWINGS The block diagram which shows the schematic structure of the electronic endoscope system provided with Example 1 of this invention. FIG. 3 is a cross-sectional view of an imaging unit in the electronic endoscope according to the first embodiment. The external view which looked at the front end surface of the front-end | tip part of the insertion part in Example 1 from the front. The front view which looked at the front end surface of the insertion part front-end | tip of the electronic endoscope of a present Example from the front. The schematic sectional drawing of the AA in FIG. The flowchart figure of an autofocus operation | movement. Sectional drawing when a treatment tool is inserted in a treatment tool channel, and a treatment tool protrudes from the front-end | tip opening. Explanatory drawing of the effect | action in the near point side of a present Example. The block diagram which shows the schematic structure of the electronic endoscope system provided with Example 2 of this invention. The external view which looked at the front end surface of the front-end | tip part of the insertion part in Example 2 of this invention from the front. The schematic sectional drawing of the BB line in FIG. The figure which shows a monitor display image when the treatment tool penetrated in the channel in Example 2 is made to protrude from a front-end | tip part. FIG. 10 is a configuration diagram illustrating a schematic configuration of an electronic endoscope system including a first modification of the second embodiment. FIG. 10 is a diagram illustrating a CPU portion in a second modification of the second embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Electronic endoscope system 2 ... Electronic endoscope 3 ... Light source device 4 ... Image processing device 5 ... Monitor 7 ... Insertion part 11 ... Tip part 14 ... Light guide 16a, 16b ... Illumination lens 17 ... Objective lens system 18 ... CCD
DESCRIPTION OF SYMBOLS 19 ... Imaging unit 21 ... Signal cable 25 ... Channel 26 ... Channel tip opening 27 ... Treatment tool insertion port 28 ... Treatment tool 31 ... Lens frame 33 ... CCD frame 37 ... Autofocus part 37a ... Brightness detection part 37b ... Contrast detection part 37c ... CPU
45 ... Lamp 47 ... Aperture 51 ... Signal converter 52 ... Image processor 54 ... Automatic dimmer 54a ... Treatment instrument detector 54b ... Luminance detector 54c ... Dimming signal generator

Claims (12)

A solid-state imaging device having a predetermined number of pixels;
An objective optical system having a predetermined viewing angle to form an image on the solid-state imaging device;
Based on a luminance signal generated from an image signal obtained when an object with white and black bands of the same width is imaged, the maximum value of the luminance signal for the white object is Imax, and the luminance signal of the black object is Imin the minimum value, when the contrast I was defined as I = (Imax-Imin) / (Imax + Imin), a predetermined value of an object disposed from the tip of the interpolation join the club at a predetermined distance spaced positions near point side of the objective optical system In order to capture with the above contrast I, the focal length variable means for driving at least a part of the lenses constituting the objective optical system and changing the focal length of the objective optical system so that the depth of field partially overlaps. When,
And the treatment instrument insertion channel that can be inserted through the treatment置具,
Have
The focal length varying means has a depth of field at which the objective optical system can capture an object having a black and white pair band pitch of 35 μm on the near point side with the contrast I of approximately 10% or more, and There is a depth of field that can be captured with the contrast I of approximately 10% or more when a subject in a black and white pair band of 0.5 mm pitch is imaged at a position where the distance from the distal end of the insertion portion is 50 mm on the far point side. And
The treatment instrument insertion channel has a distal end opening so that the distal end of the treatment instrument protruded by a predetermined distance falls within the predetermined viewing angle by the objective optical system when set to the near point side by the focal length changing means. Provided,
Under the condition that the subject of the band of the black and white pair with the 35 μm pitch can be identified with the resolving power that the contrast I is 10% or more, the black and white pair with the 35 μm pitch and the tip of the tip lens surface of the objective optical system Let d be the distance from the subject in
The ray height Lh at the distal lens surface of the objective optical system, the radius R of the distal opening of the treatment instrument insertion channel, the distance D between the optical axis of the objective optical system and the center of the distal opening, and the objective optical system When the angle of view θ that can be imaged on the solid-state imaging device,
D ≦ d / tan (90 ° −θ / 2) + Lh−R
An electronic endoscope characterized by satisfying Electronic endoscope according to claim 1, characterized in that the at least one lens constituting the front Symbol objective optical system can continuously change. Electronic endoscope according to claim 1, at least one lens constituting the front Symbol objective optical system, characterized in that said settable to two positions of the near point side and the far point side. The focal length varying means may further set at least one lens constituting the objective optical system at a third position between two positions on the near point side and the far point side. The electronic endoscope according to claim 3. The viewing angle of the imaging device including the objective optical system and the solid-state imaging device when the focal position is close-up by the focal length varying unit is 100 ° or more, and the solid-state imaging device is effective for monitor display. The electronic endoscope according to claim 1, further comprising a mosaic color filter having a number of pixels of 600,000 pixels or more . The viewing angle of the imaging device including the objective optical system and the solid-state imaging device when the focal position is close-up by the focal length varying unit is 100 ° or more, and the solid-state imaging device is effective for monitor display. electronic endoscope according to claim 1, the number of pixels and having a solid-state imaging device of black and white over 25 million pixels. The insertion unit includes an objective optical system that connects an optical image of a subject, and a solid-state image sensor that photoelectrically converts the optical image formed on the light receiving surface, the light receiving surface being disposed at a position where the objective optical system forms an image. An electronic endoscope, and an image processing device that converts an image signal from the solid-state imaging device into a video signal for display on a monitor;
In an electronic endoscope system equipped with
The luminance signal obtained when the white subject is imaged based on the luminance signal that is provided in the electronic endoscope and is generated from the video signal obtained when the white and black belt subjects having the same width are imaged. When the maximum value is defined as Imax, the minimum value of the luminance signal for the black subject is defined as Imin, and the contrast I is defined as I = (Imax−Imin) / (Imax + Imin), they are arranged at positions separated from the distal end of the insertion portion by a predetermined distance. A focal length variable means for changing the focal length of the objective optical system in order to capture the subject at a near point side of the objective optical system with a predetermined contrast I or more,
A treatment instrument insertion channel provided in the electronic endoscope and capable of inserting a treatment instrument;
Have
The focal length varying means has a depth of field at which the objective optical system can capture an object having a black and white pair band pitch of 35 μm on the near point side with the contrast I of approximately 10% or more, and There is a depth of field that can be captured with the contrast I of approximately 10% or more when a subject in a black and white pair band of 0.5 mm pitch is imaged at a position where the distance from the distal end of the insertion portion is 50 mm on the far point side. And
The treatment instrument insertion channel has a distal end opening so that the distal end of the treatment instrument protruded by a predetermined distance falls within the predetermined viewing angle by the objective optical system when set to the near point side by the focal length changing means. Provided,
Under the condition that the subject of the band of the black and white pair with the 35 μm pitch can be identified with the resolving power that the contrast I is 10% or more, the black and white pair with the 35 μm pitch and the tip of the tip lens surface of the objective optical system Let d be the distance from the subject in
The ray height Lh at the distal lens surface of the objective optical system, the radius R of the distal opening of the treatment instrument insertion channel, the distance D between the optical axis of the objective optical system and the center of the distal opening, and the objective optical system When the angle of view θ that can be imaged on the solid-state imaging device,
D ≦ d / tan (90 ° −θ / 2) + Lh−R
An electronic endoscope system characterized by satisfying The electronic endoscope system according to claim 7, wherein at least one lens constituting the objective optical system is moved . According to claim 7, further comprising a focus control means for setting the solid based on the output signal of the image pickup device generates a control signal for controlling the focal length changing means, said focusing the objective optical system condition Electronic endoscope system. Tip opening of the channel, to claim 7, characterized that you have been arranged so as to face the broad direction of the display area in the display area for displaying an optical image imaged by the solid-state image pickup element on the monitor The electronic endoscope system described. The viewing angle of the imaging device including the objective optical system and the solid-state imaging device when the focal position is close-up by the focal length varying unit is 100 ° or more, and the solid-state imaging device is effective for monitor display. The electronic endoscope system according to claim 7 , further comprising a mosaic color filter having a number of pixels of 600,000 pixels or more . The viewing angle of the imaging device including the objective optical system and the solid-state imaging device when the focal position is close-up by the focal length varying unit is 100 ° or more, and the solid-state imaging device is effective for monitor display. 8. The electronic endoscope system according to claim 7 , further comprising a black and white solid-state imaging device having 250,000 pixels or more .

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