KR100848443B1 - Endoscope and endoscope device - Google Patents

Abstract

An object of the present invention is to provide an endoscope and an endoscope apparatus capable of performing a smooth approach to a screening and desired magnification observation site and capable of magnifying and observing close to 3 to 4 mm to a subject without complicated operation such as zooming. Therefore, this endoscope is provided with the fixed-focus imaging unit comprised with the objective optical system 5 and the solid-state image sensor 1 of the color in which the color filter is arrange | positioned for every image, and a solid-state image sensor is the conditional expression (1). (300 <IH / P <550), the objective optical system satisfies Condition (2) (300 <FI / P <550) and Condition (3) (2400 × P <Fno. <4200 × P), The MTF on the optical axis at the spatial frequency 1 / (3 × P) at the object distance 4 mm of the objective optical system and the MTF on the optical axis at the spatial frequency 1 / (3 × P) at the object distance 50 mm were both 10. Arrange the imaging surface of the solid-state imaging device at a position of at least% The configuration includes the image pickup unit of a fixed focus type.

Endoscope, Screening, Objective Optics, Imaging Unit, Fixed Focus

Description

Endoscope and endoscope devices {ENDOSCOPE AND ENDOSCOPE DEVICE}

TECHNICAL FIELD The present invention relates to an endoscope and an endoscope apparatus, and more particularly, to an electronic endoscope provided with a fixed focus imaging unit constituted by an objective optical system and a solid-state imaging device.

The endoscope provided with a so-called fixed focus imaging unit in which a solid-state imaging device is fixed at an image optical position of the objective optical system and does not have a movable portion can make the structure of the imaging unit simple and small, thereby reducing costs and reducing the outer diameter of the endoscope insertion portion. It is advantageous in terms of thinning and shortening the length of the tip hard part. Moreover, since there is no need of focusing, a user can concentrate on operation of an endoscope and it becomes easy to handle, and it is used widely in each field, such as medical use and industrial use.

The endoscope provided with such a fixed-focus imaging unit can be operated to guide the endoscope insertion part to the part to be observed, and to perform so-called screening to select a desired observation part while viewing a wide range. In general medical endoscopes, the focus position for obtaining a clear image is set even at about 50 to 100 mm). In addition, when the distance between the endoscope insertion portion and the object is close, the object distance from which a clear image is obtained is generally up to about 5 to 10 mm.

In the case where the subject is to be enlarged and the object is to be observed in detail, it is conceivable to include a so-called zoom type imaging unit capable of performing a zooming operation (zooming) in which the lens in the objective optical system is changed to change the focal length and the working distance. . For the endoscope provided with such a zoom type imaging unit, various proposals have been made in the past by, for example, Japanese Patent Application Laid-Open No. 2000-330015, Japanese Patent Application Laid-Open No. 2001-33710, and the like.

In an endoscope provided with a zoom imaging unit, a depth of field almost the same as that of an endoscope provided with a fixed focus imaging unit at a so-called wide end is obtained. Therefore, in this case, the same use method as the endoscope provided with the fixed-focus imaging unit is possible. In addition, in the so-called remote end where the focal length is long, the depth of focus is biased toward the proximal side compared to the wide end, so that the focus is blurred at a far diameter (about 50 to 100 mm). Instead, a clear image is obtained when the distance between the endoscope front end insertion portion and the subject is close (for example, about 2 mm to 3 mm in an endoscope provided with a general zoom type imaging unit). Therefore, the detailed observation can be performed by enlarging the subject.

In the endoscope provided with the above-mentioned fixed-focus imaging unit, when there is a part which you want to enlarge and observe in detail, even if the endoscope insertion part is close to the part (subject), a focus is obtained before sufficient magnification or resolution is obtained. There is a problem that becomes cloudy.

In the case of the endoscope provided with the above-described zoom type imaging unit, it is possible to magnify the subject and perform detailed observation by performing a zoom operation. However, after performing observation at the wide end, the approach to the portion to be magnified and observed is performed. This requires manipulation to move the variator lens. Therefore, there exists a subject that operation becomes complicated compared with the endoscope provided with the fixed-focus imaging unit.

In addition, the endoscope provided with the zoom type imaging unit described above has a problem in that it becomes difficult to handle the endoscope because the depth of focus of the objective optical system becomes very narrow, ie, the depth of field of the objective optical system becomes very narrow at the time of magnification observation at the remote end.

In addition, since the endoscope provided with the zoom type imaging unit described above requires a mechanism for moving the variator lens, the imaging unit is larger than the fixed focus type imaging unit. There is a problem that will grow. In addition, since the structure including the mechanism for moving the variator becomes complicated and the number of parts increases, there is a problem that the manufacturing cost is higher than that of the fixed focus imaging unit.

In the endoscope provided with the zoom type imaging unit described above, when the treatment tool is treated after the enlargement observation, the viewing angle becomes narrow at the remote end, so that the treatment tool becomes difficult to enter the field of view. It is necessary to carry out treatment after separating the observation distance by moving. That is, since the operator must perform the operation of guiding the distal end of the endoscope insertion part to the position to be desired, the operation of zooming, and the operation of the treatment instrument, there is a problem that the operation becomes very complicated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described points, and its object is to enable observation of a far-field, to smoothly approach an area to be screened and enlarged, and to perform complicated operations such as zooming. Magnification observation can be performed in close proximity to a subject of about 3 to 4 mm without subjecting the subject, and treatment by the treatment instrument can be performed while performing magnification observation, and added to suppress large hardening of the outer diameter of the insertion part. While providing an endoscope and an endoscope apparatus that can contribute to a reduction in manufacturing cost.

In order to achieve the above object, the endoscope of the present invention is an endoscope including an objective optical system and a fixed-focus imaging unit composed of a solid-state imaging element of color in which color filters are arranged for each pixel, and the imaging unit includes:

Conditional Expression (1) 300 <IH / P <550

P: horizontal pixel pitch [mm] of a solid-state image sensor

IH: About a solid-state image sensor which satisfy | fills the distance [mm] from the center in the display area of a solid-state image sensor to the furthest position, and pixel pitch [P (mm)] of a solid-state image sensor,

Conditional Expression (2) 300 <Fl / P <550

Fl: Focal length of the objective optical system [mm]

And

Conditional Expression (3) 2400 × P <Fno. <4200 × P

Fno. : Effective F number of objective optical system

It consists of an objective optical system of a characteristic satisfying

The MTF on the optical axis at the spatial frequency 1 / (3 × P) at the object distance 4 mm of the objective optical system and the MTF on the optical axis at the spatial frequency 1 / (3 × P) at the object distance 50 mm were both 10. It is characterized by the imaging surface of a solid-state image sensor arrange | positioned at the position used to be% or more.

In addition, the endoscope device of the present invention is a fixed focus composed of a color filter disposed for each pixel, and further comprising a solid-state image sensor that satisfies the conditional expression (1) and an objective optical system that satisfies the conditional expression (2) and the conditional expression (3). An endoscope including an imaging unit of a formula and at least display means for displaying an image acquired by the imaging unit, and the range at the object side of the imaging unit having a resolution of 25 or more / mm at the center of the image displayed on the display means. When d1 is a range on the object side of the imaging unit whose resolution at the center of the image displayed on the display means is 2 / mm or more, d2, the position of 3.5 mm from the most object side surface of the objective optical system constituting the imaging unit. The focal point on the optical axis at is contained in both d1 and d2 and is located at a position of 50 mm from the most object side surface of the objective optical system constituting the imaging unit. An object point on the optical axis is characterized in that which is the imaging surface of the solid-state image sensor arranged near the imaging position of the objective optical system so that it includes only d2.

In the endoscope apparatus of the present invention, an image of an object is formed by an objective optical system satisfying the conditional expression (2) and the conditional expression (3), and a color filter is arranged for each pixel in the vicinity of the image plane of the objective optical system. The endoscope apparatus is provided with the fixed-focus imaging unit which acquires an image signal by the solid-state image sensor which satisfy | fills the conditional formula (1), and the circuit system which processes the image signal conveyed from a solid-state image sensor, The endoscope apparatus is a It has a resolution of 35 µm or more when the distance from the objective optical system to the object is 4 mm, and has a resolution of 0.45 mm or more when the distance from the objective optical system to the object is 50 mm.

Moreover, the endoscope of this invention is an endoscope provided with the objective optical system and the fixed-focus imaging unit comprised with the solid-state image sensor which a luminance signal is produced for every pixel, The said imaging unit is

Conditional Expression (4) 200 <IH / P <360

P: horizontal pixel pitch [mm] of a solid-state image sensor

IH: About a solid-state image sensor which satisfy | fills the distance [mm] from the center in the display area of a solid-state image sensor to the furthest position, and pixel pitch [P (mm)] of a solid-state image sensor,

Conditional Expression (5) 200 <Fl / P <360

Fl: Focal length of the objective optical system [mm]

And

Conditional Expression (6) 1600 × P <Fno. <2800 × P

Fno. : Composed of objective optical system satisfying effective F number of objective optical system,

The MTF on the optical axis at the spatial frequency 1 / (2 × P) at the object distance of 4 mm and the MTF on the optical axis at the spatial frequency 1 / (2 × P) at the object distance of 50 mm were both 10. It is characterized by the imaging surface of a solid-state image sensor arrange | positioned at the position used to be% or more. In addition, the endoscope apparatus of the present invention comprises a solid-state imaging device for generating a luminance signal for each pixel and satisfying the conditional expression (4), and an objective optical system satisfying the conditional expression (5) and the conditional expression (6). An endoscope apparatus comprising at least an endoscope including at least a fixed focus imaging unit, and display means for displaying an image acquired by the imaging unit, the endoscope apparatus having a resolution of 25 at the center of an image displayed on the display means. When the range on the object side of the imaging unit of mm or more is set to d1, and the range on the object side of the imaging unit of 2 / mm or more of resolution at the center (on the optical axis) of the image displayed on the display means is set to d2. The object point on the optical axis at a position of 3.5 mm from the surface on the object side of the objective optical system to be included in both d1 and d2, The imaging surface of the solid-state imaging device is arranged near the imaging position of the objective optical system so that the object point on the optical axis at the position of 50 mm from the surface on the object side is included only in d2.

In the endoscope apparatus of the present invention, an image of an object is formed by an objective optical system satisfying the conditional expression (5) and the conditional expression (6), and a color filter is arranged for each pixel in the vicinity of the image plane of the objective optical system. It is an endoscope apparatus provided with the fixed-focus imaging unit which acquires an image signal by the solid-state image sensor which satisfy | fills the said conditional formula (4), and the circuit system which processes the image signal conveyed from a solid-state image sensor, This endoscope apparatus Has a resolution of 35 µm or more when the distance from the objective optical system to the object is 4 mm, and has a resolution of 0.45 mm or more when the distance from the objective optical system to the object is 50 mm.

Here, the definition of the resolution will be described.

When the point image is formed by an optical system having a circular opening of approximately aberration, the image of the object becomes an Airy disk which is a diffraction image of the circular opening. When two points having the same intensity approach each other, these diffraction images overlap with each other, resulting in an intensity distribution as shown in FIG.

Fig. 4 is a diagram showing the intensity distribution on a straight line passing through the intensity centers of two diffraction images, where the horizontal axis represents distance (unit: mm) and the vertical axis represents intensity (arbitrary unit). Rayleigh (life) set the limit when the two diffraction images could be distinguished into two when the distance between the two diffraction images coincided with the radius of the Airy disk. Since then, this has become one criterion called Rayleigh criterion. At this time, the intensity distribution of the diffraction image is left in a state having a 74% intensity relative to the peak (between Asakura Bookstore: "Optical Technology Handbook").

Here, in the present invention, the resolution of the distribution intensity between the two points is 74% or less with respect to the apex and the resolution is defined as the "resolution".

Specifically, as shown in Fig. 5, the two points placed before the objective optical system 5 disposed on the distal end portion of the endoscope 4 have two points in the horizontal direction on the imaging surface of the solid-state imaging device 1. The output signal from the circuit system 6 which processes the image signal from the solid-state image sensor 1 and image | photographs so that it may be arranged (that is, two dot phases will be arranged horizontally on the screen of the monitor 7) will be oscilloscope 9 ), And the intensity distribution of two points is measured. At this time, the minimum distance between two points of "resolution" is referred to as "resolution".

At this time, as shown in Fig. 6, the two points can be substituted with black and white line pairs arranged in the horizontal direction. In the present invention, the term "resolution" refers to a value obtained by the above method.

Next, resolution is defined as follows.

In Fig. 6, a black and white line pair placed before the objective optical system 5 disposed at the distal end portion of the endoscope 4 is imaged so that black and white bands are arranged in a horizontal direction on the imaging surface of the solid-state imaging device 1; The monitor 7 passes the circuit system 6 that processes the image signal transferred from the solid-state imaging device 1 and displays it on the monitor 7. At this time, the intensity distribution of black and white obtained on the screen of the monitor 7 is as shown in FIG.

Fig. 7 is a diagram showing signal waveforms when the horizontal image signal output from the monitor 7 is captured by an oscilloscope (not shown in Fig. 6), and the horizontal axis indicates the position in the horizontal direction on the monitor screen. Indicates signal strength, respectively.

Here, when the maximum value of the intensity distribution shown in Fig. 7 is set to Imax and the minimum value to Imin, the contrast I on the monitor of the black and white line pair is

I = (Imax-Imin) / (Imax + Imin)... (i)

Obtained by

The resolution is defined as the inverse of the width of the black and white line pair when the above-mentioned contrast (I) becomes 10%.

Therefore, in the above-described techniques of "25 resolutions / mm or more" and "2 resolutions / mm or more", the contrast of monochrome line pairs having a width of 40 µm or less and a width of 0.5 mm or less is 10% or more on the monitor. It is pointing.

In addition, in this invention, "MTF" shall indicate the average value of MTF in each wavelength of d line (wavelength 587.6 nm), e line (wavelength 546.1 nm), and f line (wavelength 486.1 nm).

In addition, the "display area" and "IH" of a solid-state image sensor are demonstrated here briefly.

The endoscope apparatus is mainly comprised by the endoscope 4, the circuit system 6 which processes an image signal, and the image display monitor 7, as shown in FIG. The image picked up by the imaging unit composed of the objective optical system 5 and the solid-state imaging element 1 is processed by the circuit system 6 which processes the image signal and displayed on the image display monitor 7. "Display area" of the solid-state image sensor 1 refers to the area | region on the solid-state image sensor 1 corresponding to the range displayed on the image display monitor 7 mentioned above.

Therefore, when the display range on the image display monitor 7 is limited by the octagonal field mask, the display area formed on the effective pixel area 2 of the solid state imaging element 1 as shown in FIG. (3) also has the same shape.

As another example, when the display range on the image display monitor 7 is limited to the circumferential shape only in the left and right directions, as shown in FIG. 2, on the effective pixel region 2 of the solid-state imaging element 1. The formed display area 3 also has the same shape.

In addition, when the full screen is displayed on the image display monitor 7 without a visual field mask, the effective pixel area 2 of the solid-state imaging element 1 corresponding to the shape of the display portion of the image display monitor 7 is the display area. Becomes

In addition, "IH" points out the distance from the center of the display area of the solid-state image sensor 1 to the furthest position. This is commonly called phase height.

Next, the definition of the depth of field will be briefly described here.

In a general endoscope, the case where the solid-state image sensor of the pixel pitch P is arrange | positioned at the upper surface position Xb 'when the best distance is made into Xb is considered. Under conditions where the solid-state imaging device is fixed, when the object is moved to Xn, the upper surface position Xn 'at the time of proximity is shifted from the imaging surface position of the solid-state imaging device.

At this time, when the largest confusion source that can be considered to be correct is considered as an allowable confusion source and its diameter is δ, when it can be recognized that the diameter of the confusion circle on the image pickup surface of the solid-state imaging element is smaller than δ, Xn to Xn Objects up to can be considered to be correct. That is, the range until the confusion circle diameter matches δ can be defined as the depth of field on the proximal side.

At this time, the following equation is established from Newton's phase open expression.

(1 / Xn)-(1 / Xb) = δ Fno./Fl ² ... (Ii)

Similarly, the esophagus on the origin side of the depth of field is defined as follows.

(1 / Xb)-(1 / Xf) = δ Fno./Fl ² ... (Ⅲ)

If we put together equation (ii) and (iii),

(1 / Xn)-(1 / Xf) = 2δFno. / Fl ² ... (Ⅵ)

Becomes However, the best distance is Xb, the distance to the depth-of-field near point is Xn, the distance to the depth-of-field origin is Xf, the allowable confusion circle diameter is δ, the focal length of the optical system is Fl, and the effective F number of the optical system is Fno. .

The above Conditional Expressions (1) and (4) define the conditions of the solid-state imaging device to be used in the present invention, and indicate a range in which the ratio of the pixel pitch of the solid-state imaging device to the maximum image height should be present.

In general, since the allowable confusion circle diameter δ is proportional to the pixel pitch of the solid-state imaging element, the larger the value of IH / P, the smaller the δ with respect to the image height IH. For this reason, when the value of IH / P becomes too large, a wide depth of field will not be obtained and the objective of this invention will not be achieved.

On the other hand, when the value of IH / P decreases, the depth of field becomes wider, but the pixel pitch of the solid-state image sensor with respect to the image height IH increases, so that the sampling interval of the solid-state image sensor becomes long. Therefore, the resolution with respect to the image of a constant magnification falls. If the value of IH / P is too small, the required resolution cannot be obtained even at a recent point in the depth of field, or it must be very close to the object to obtain the required resolution, and the object of the present invention cannot be achieved.

Therefore, according to this invention, in the imaging unit using the solid-state image sensor of the color in which the color filter was arrange | positioned for every pixel, it is preferable to use the solid-state image sensor which satisfy | fills conditional formula (1).

In addition, in the imaging unit using the solid-state imaging device in which the luminance signal is generated for each pixel, it is preferable to use the solid-state imaging device that satisfies the conditional formula (4).

On the other hand, the conditional expressions (2) and conditional expressions (5) define the focal lengths of the objective optical system combined with the solid-state imaging device defined by the conditional expressions (1) and (4).

As can be seen from the above formula (iii), when the focal length Fl of the objective optical system becomes larger, the depth of field becomes narrower.

As an objective optical system combined with the solid-state imaging device defined by the above Conditional Expressions (1) and (4), when Fl exceeds the upper limit of the Conditional Expressions (2) and (5), the depth of field narrows, and the magnification sufficient at the near point is obtained. Or the resolution will not be obtained or the focus will be blurred at a distance, and the object of the present invention cannot be achieved.

Next, the lower limit of conditional expression (2) and conditional expression (5) is demonstrated.

In an endoscope apparatus including an imaging unit in which an imaging surface of a solid-state imaging device is disposed in the vicinity of an image plane of an objective optical system, and a circuit system for processing an image signal transferred from the solid-state imaging device, the endoscope apparatus passes through the objective optical system to provide a solid-state imaging device. When two points are formed on the imaging surface, the minimum distance on the solid-state imaging device in which the two points are resolved on the output signal from the above-described circuit system indicates the pixel pitch of the solid-state imaging device and the image signal transferred from the solid-state imaging device. It is determined by the characteristics of the circuit system to be processed. At this time, if the coefficient determined by the characteristics of the circuit system is K and the pixel pitch of the solid-state imaging device is P, the minimum distance described above is represented by KP.

In general, when the focal length of the optical system is Fl and the front focal position of the optical system is fF, the imaging magnification β by the optical system of the subject placed at the object distance X is

β = Fl / (X + fF)... (v)

Therefore, the distance KP on the imaging surface of the solid-state imaging device is KP / β on the object side.

In the endoscope device comprising an imaging unit having a solid-state imaging element and a circuit system for processing an image signal transferred from the solid-state imaging element, how much finer resolution is resolved, so X = Xn (Xn: depth of field). Distance to the near point), the resolution of the endoscope apparatus at the near point must be correct. If we set this value to R,

R = KP (Xn + fF) / Fl... (Ⅵ)

Represented by

From equation (vi), when the value of focal length Fl becomes small, the value of R becomes large.

Depth of field as the objective optical system combined with the solid-state image sensor of the pixel pitch P prescribed | regulated by the above-mentioned conditional expression (1) and conditional formula (4), if Fl exceeds the lower limit of the above-mentioned conditional expression (2) and conditional expression (5). In the innermost point Xn, since the value of the resolution R becomes too large and a minute thing becomes invisible, the objective of this invention cannot be achieved.

Therefore, in the imaging unit using the solid-state image sensor of the color in which the color filter is arrange | positioned for every pixel, it is preferable to use the objective optical system of the focal length which satisfies the above-mentioned conditional expression (2) with respect to the pixel pitch P.

In addition, in the imaging unit using the solid-state imaging element in which the luminance signal is generated for each pixel, it is preferable to use the objective optical system having the focal length that satisfies the conditional expression (5) described above with respect to the pixel pitch P.

On the other hand, the conditional expressions (3) and (6) described above define the effective F number of the objective optical system combined with the solid-state imaging device defined by the conditional expressions (1) and (4).

It is known that when imaging by a lens, light is affected by diffraction. The larger the Fno., The larger the point image is due to the effect of diffraction. If the point exceeds the limit of the size of the point image, no matter how much the focus is adjusted, the thin part of the subject will appear blurred. This limit is defined by Rayleigh as the distance of the limit which can be identified as a separate image when two points approach each other. When λ is the wavelength of light and Fno. Is an effective F number, 1.22. Denoted by.

In the combination of the solid-state imaging device defined by the above Conditional Expressions (1) and (4) and the objective optical system specified by the above Conditional Expressions (2) and (5), if Fno. Exceeds the upper limit of the Conditional Expression, Even if it is set to, the thin part of the subject appears to be blurred, and the object of the present invention cannot be achieved.

In addition, as can be seen from the above equation (i), when the value of Fno. Decreases, the depth of field becomes narrower.

In the combination of the solid-state imaging device defined in the above Conditional Expressions (1) and (4) and the objective optical system specified in the above Conditional Expressions (2) and (5), if Fno. Exceeds the lower limit of the Conditional Expression, the depth of field Becomes narrow, sufficient magnification or resolving power cannot be obtained at the near point, or the focus is blurred at the far-field, and the object of the present invention cannot be achieved.

Therefore, in the imaging unit using the solid-state image sensor of the color in which the color filter is arrange | positioned for every pixel, it is preferable to use the objective optical system of the effective F number which satisfy | fills the above-mentioned conditional expression (3) with respect to the pixel pitch P.

In addition, in the imaging unit using the solid-state imaging device in which the luminance signal is generated for each pixel, it is preferable to use the objective optical system of the effective F number that satisfies the conditional expression (6) described above with respect to the pixel pitch (P).

In addition, if the above-mentioned condition (1), condition (2), and condition (3) are comprised so that one or all may satisfy | fill following condition (1) ', condition (2)', and condition (3) ', The balance of the magnification and resolution of the imaging unit is good, and more suitable.

Conditional Expression (1) '390 <IH / P <510

Conditional Expression (2) '390 <Fl / P <510

Conditional Expression (3) '3000 × P <Fno. <4200 × P

In addition, if the above-mentioned condition (4), condition (5), and condition (6) are comprised so that one or all may satisfy | fill following condition (4) ', condition (5)', condition (6) ', The balance of the magnification and resolution of the imaging unit is good, and more suitable.

Conditional Expression (4) '260 <IH / P <340

Conditional Expression (5) '260 <Fl / P <340

Conditional Expression (6) '2000 × P <Fno. <2800 × P

It is essential that the endoscope according to the present invention is constituted by a solid-state imaging device and an objective optical system that satisfy the above-mentioned conditions, but it is also necessary to define the imaging surface position of the solid-state imaging device disposed in the vicinity of the image plane of the objective optical system.

In the case of using a solid-state imaging device of a color in which a color filter is arranged for each pixel, when the MTF on the optical axis at the spatial frequency 1 / (3 × P) is 10% or more, the confocal circle diameter does not exceed the permissible constellation circle diameter and the depth of field Since the optical axis of the imaging surface of the solid-state image sensor and the objective optical system is perpendicular to each other, and the MTF on the optical axis at spatial frequency 1 / (3 x P) at an object distance of 4 mm, and an object distance of 50 mm It is preferable to arrange | position the imaging surface of the said solid-state imaging element in the position where all MTF on an optical axis in spatial frequency 1 / (3 * P) of the above becomes 10% or more.

Alternatively, in the case of using a solid-state imaging device in which a luminance signal is generated for each pixel, when the MTF on the optical axis at the spatial frequency 1 / (2 × P) is 10% or more, the diameter of the confusion circle does not exceed the allowable confusion circle diameter, Since it can be regarded as the depth, the optical axis of the imaging surface of the solid-state imaging device and the objective optical system are perpendicular to each other, and the MTF on the optical axis at the spatial frequency 1 / (2 x P) at an object distance of 4 mm, and an object distance of 50 mm. It is preferable to arrange | position the imaging surface of the said solid-state image sensor in the position where all MTF on the optical axis in spatial frequency 1 / (2 * P) becomes 10% or more.

Alternatively, the combination of the solid-state image sensor and the objective optical system of a color in which a color filter is arranged for each pixel well suited to the above conditional expression (1), conditional expression (2) and conditional expression (3), or conditional expression (4) and conditional expression (5) ), Which is composed of a combination of a solid-state image sensor and an objective optical system in which a luminance signal is generated for each pixel that satisfies Conditional Expression (6), and the image plane of the solid-state image sensor and the optical axis of the objective optical system are perpendicular to each other on the optical axis (image center). When the range of the object side with the resolution of 25 / mm or more is d1 and the range of the object side with the resolution of 2 / mm or more on the optical axis (image center) is d2, it is determined from the distal end surface of the objective optical system on the optical axis. It is preferable to arrange the imaging surface of the solid-state imaging device at a position where the object point at the position of mm is included in both d1 and d2, and the object point at the position of 50 mm from the distal end surface of the objective optical system on the optical axis is included only in d2. The.

The imaging surface of the solid-state imaging element so that the object point at the position of 3.5 mm is included in the range d2 on the object side having a resolution of 2 or more / mm or more, and included in the range d1 on the object side having a resolution of 25 or more / mm or more. By arranging, the microscopic structure of biological tissues such as a colonic pit pattern can be observed, for example, in a medical endoscope device, it is useful when accurate diagnosis or treatment of a lesion is performed.

In addition, since an object at a position of 50 mm is included in the range d2 on the object side having a resolution of 2 / mm or more, a clear image is obtained even when observing the far field, so that screening is performed while observing the inside of a living body extensively. At the same time, the operation of guiding the endoscope insertion portion to the portion where the end portion is desired can be easily performed.

Alternatively, the combination of the solid-state image sensor and the objective optical system of a color in which a color filter is arranged for each pixel well suited to the above conditional expression (1), conditional expression (2) and conditional expression (3), or conditional expression (4) and conditional expression (5) ), When the solid-state imaging device and the objective optical system in which the luminance signal is generated for each pixel that satisfies the conditional formula (6) are formed, and the image plane of the solid-state imaging device and the optical axis of the objective optical system are perpendicular to the object distance of 4 mm. It is preferable to arrange the imaging surface of the solid-state imaging device at a position having a resolution of 35 µm or more and a resolution of 0.45 mm or more when the object distance is 50 mm.

By having a resolution of 35 µm or more at an object distance of 4 mm, for example, in a medical endoscope device, the microstructure of a living tissue such as a large intestine pit pattern can be observed, which is useful when accurate diagnosis or treatment of a lesion is performed. .

In addition, at an object distance of 50 mm, having a resolution of 0.45 mm or more, a clear image is obtained even when observing a far field. Therefore, screening is performed while observing the inside of a living body extensively, and guided to a portion where the endoscope insertion part is to be observed. Operation can be easily performed.

By arranging the objective optical system and the solid-state image sensor in the form described above, a clear image having a wide depth of field continuously from the far-field to the near point and having high resolution at an easy-to-use distance such as 3 to 4 mm can be obtained.

In addition, when the treatment channel such as a biopsy potato is projected by passing the treatment channel to a distance of 4 mm from the endoscope insertion portion, the imaging unit and the treatment channel are disposed so that at least a portion of the treatment instrument falls within the field of view of the imaging unit. While observing the microstructure of the living tissue, the tissue can be collected and the like. Thereby, the treatment precision of a lesion part can be improved.

By setting it as the above-mentioned structure, the endoscope according to this invention can acquire the following effects.

ㆍ Easy to insert and screen scope because of the observable

ㆍ Because the distance can be observed, the approach to the area to be magnified can be smoothly performed.

A magnified image with high resolution can be obtained at an easy-to-use distance such as 3 to 4 mm

ㆍ It is difficult to miss the subject because the far side is continuously within the depth of field when zoomed in.

ㆍ Easy operation because complicated operation such as zooming is unnecessary

Since the imaging unit has no moving parts, the outer diameter of the insert can be made thin

ㆍ Since the imaging unit has no moving parts, manufacturing cost can be kept low

Since the treatment tool enters the field of view while observing the magnified image, the treatment with high accuracy can be performed.

As described above, according to the present invention, since a distant view can be observed, a smooth approach can be performed to a site to be screened and magnified, and about 3 to 4 mm without subjecting a complicated operation such as zooming. The magnified observation can be performed in close proximity, and the treatment tool can be carried out while the magnified observation is performed, so that an endoscope and an endoscope apparatus having a low manufacturing cost with a small external diameter of the insert can be provided.

1 is an explanatory diagram of a display area of a solid-state imaging device.

2 is an explanatory view of a display area of another solid-state imaging device.

3 is a conceptual diagram of the configuration of the endoscope apparatus.

4 is an explanatory view of the definition of the resolution.

5 is an explanatory diagram of a method for measuring resolution.

6 is an explanatory diagram of another measuring method of resolution.

7 is an explanatory view of the definition of the resolution power.

8 is a cross-sectional view of an objective optical system of the first embodiment of the present invention.

Fig. 9 is a sectional view of the imaging unit of the first embodiment of the present invention.

Fig. 10 is a view of the endoscope inserting portion of the first embodiment of the present invention as seen from its distal end;

Figure 11 is a sectional view of the endoscope insertion portion of the first embodiment of the present invention.

Fig. 12 is a sectional view of the objective optical system of the second embodiment of the present invention.

Fig. 13 is a sectional view of the objective optical system of the third embodiment of the present invention.

Fig. 14 is a sectional view of the objective optical system of the fourth embodiment of the present invention.

Fig. 15 is a sectional view of the objective optical system of the fifth embodiment of the present invention.

Fig. 16 is a sectional view of the objective optical system of the first conventional example.

Fig. 17 is a sectional view of the objective optical system of the second conventional example.

Fig. 18 is an explanatory diagram of a solid-state imaging device in which an array of pixels is arranged with a 1/2 horizontal pitch blurred for each line in the horizontal direction.

As an example of the endoscope of this invention, the data of an objective optical system and the data of a solid-state image sensor are shown. Where IH is the maximum image height, P is the pixel pitch of the solid-state image sensor, Fl is the focal length of the objective optical, Fno. Is the aperture ratio, 2ω is the viewing angle, R is the radius of curvature of each lens surface, and D is the thickness of each lens. And the lens spacing, Ne represents the refractive index in the e-ray, and Vd represents the Abbe's number.

For comparison, two examples of data are shown below as the objective optical system and the solid-state imaging device of the conventional endoscope.

[First Conventional Example]

Solid-state imaging device in which a luminance signal is generated for each pixel

IH = 0.76 mm P = 0.0044 mm IH / P = 173

Objective optical system

Fl = 0.77698 mm Fno. = 6.457 2ω = 133.6 °

Fl / P = 177 1600 × P = 6.4 2800 × P = 11.2

Fig. 16 is a sectional view of the objective optical system of the first conventional example.

The first conventional example is an example of a conventional endoscope apparatus using a solid-state imaging element in which a luminance signal is generated for each pixel.

The maximum resolution is 24 pieces / mm at an object distance of 3.0 mm, and does not have a range of 25 or more resolutions. The range of the object side whose resolution on an optical axis is 2 / mm or more is 0-33 mm.

The resolution when the object distance is 4 mm is 49 µm and the resolution when the object distance is 50 mm is 0.57 mm. The depth of field is from 3.0 mm to infinity (∞).

The first conventional example is a case where the range of the conditional expression (4) and the conditional expression (5) is less than. In this case, the depth of field is wide, but compared with the same object distance, the resolution is lower than that of the endoscope apparatus according to the present invention.

If the Fno. Is made larger, the depth of field on the proximal side is further increased, and if the object is approached, a higher resolution can be obtained, but at that time, the distance of the object becomes too close, making it difficult to handle. In addition, the treatment instrument does not enter the field of vision at the time of magnification observation.

Second Conventional Example

Solid-state image sensor of color with a color filter arranged for each pixel

IH = 1.24 mm P = 0.00205 mm IH / P = 605

Objective optical system

Fl = 1.29838 mm Fno. = 8.532 2ω = 141.6 °

Fl / P = 633 2400 × P = 5.28 4200 × P = 9.24

Fig. 17 is a sectional view of the objective optical system of the second conventional example.

The second conventional example is an example of a conventional endoscope apparatus using a solid-state image sensor of color in which color filters are arranged for each pixel.

The range of the object side with the resolution of 25 / mm or more on the optical axis is 5.8-8.0 mm, and the range of the object side with the resolution of 2 / mm or more on the optical axis is 0-100 mm. In addition, the object distance of 4 mm is outside the depth of field. The resolution when the object distance is 50 mm is 0.25 mm. The depth of field is 6.5 to 50 mm.

The second conventional example is a case where it exceeds the range by the above-mentioned conditional expression (1) and conditional expression (2). Compared with the same object distance, the resolution is higher than that of the endoscope according to the present invention, but since the depth of field becomes narrower, focus blur occurs when the subject approaches.

If Fno. Is made larger, the contrast of the image in the depth of field will be reduced because the size of the diffraction image by the objective optical system exceeds the allowable confusion circle of the solid-state imaging element. Therefore, even if there is a part to be enlarged, if it is approached, the focus becomes blurred, and the object of the present invention cannot be achieved.

Next, the data of the Example of this invention is shown.

[First Embodiment]

Solid-state image sensor of color with a color filter arranged for each pixel

IH = 1.442 mm P = 0.003 mm IH / P = 481

Objective optical system

Fl = 1.47866 mm Fno. = 11.710 2ω = 132.3 °

Fl / P = 493 2400 × P = 7.2 4200 × P = 12.6

8 is a sectional view of the objective optical system of the first embodiment.

The first embodiment is an embodiment of a medical endoscope apparatus using a solid-state imaging device of color in which a color filter is arranged for each pixel.

The MTF on the optical axis at the spatial frequency 1 / (3 x P) at an object distance of 4 mm is 12.6%, and the MTF on the optical axis at the spatial frequency 1 / (3 x P) at an object distance of 50 mm is 10.8%. .

Moreover, the range of the object side which is 25 / mm or more of resolution on the optical axis is 3.2-5.5 mm, and the range of the object side which is 2 / mm or more of resolution on the optical axis is 0-80 mm.

The resolution when the object distance is 4 mm is 29 µm and the resolution when the object distance is 50 mm is 0.31 mm.

Accordingly, the endoscope apparatus according to the first embodiment satisfies the following conditions.

That is, in an endoscope provided with a fixed focus imaging unit composed of an objective optical system and a solid-state imaging device of color in which color filters are arranged for each pixel, the solid-state imaging device satisfies conditional expression (1), and the objective optical system has a conditional expression ( 2) and conditional expression (3), MTF on the optical axis at spatial frequency 1 / (3 x P) at the object distance of 4 mm of the objective optical system, and spatial frequency 1 / (3 at the object distance of 50 mm The imaging surface of a solid-state image sensor is arrange | positioned in the position where all MTF on an optical axis in xP) becomes 10% or more.

Conditional Expression (1) 300 <IH / P <550

Conditional Expression (2) 300 <Fl / P <550

Conditional Expression (3) 2400 × P <Fno. <4200 × P

only,

P: horizontal pixel pitch [mm] of a solid-state image sensor

IH: distance from the center in the display area of the solid-state image sensor to the furthest position [mm]

Fl: Focal length of the objective optical system [mm]

Fno. : Effective F number of objective optical system

In addition, the endoscope apparatus which concerns on a 1st Example satisfy | fills the following conditions.

That is, in an endoscope apparatus including an endoscope including at least a fixed-focus imaging unit and display means for displaying an image acquired by the imaging unit, in the imaging unit, a color filter is arranged for each pixel, and the conditional expression (1) The solid-state image sensor which satisfies, and the objective optical system which satisfy | fills conditional formula (2) and conditional formula (3), and the range in the object side of the said imaging unit whose resolution in the center of the image displayed on a display means is 25 pieces / mm or more. When d1 is a range on the object side of the imaging unit whose resolution at the center of the image displayed on the display means is 2 / mm or more, d2, it is 3.5 mm from the most object side surface of the objective optical system constituting the imaging unit. The object point on the optical axis at the position is included in both d1 and d2, and the object point is located at a position of 50 mm from the surface of the object side of the objective optical system constituting the imaging unit. The imaging surface of the solid-state imaging element is disposed near the imaging position of the objective optical system so as to be included only in silver d2.

Conditional Expression (1) 300 <IH / P <550

Conditional Expression (2) 300 <Fl / P <550

Conditional Expression (3) 2400 × P <Fno. <4200 × P

only,

P: horizontal pixel pitch [mm] of a solid-state image sensor

IH: distance from the center in the display area of the solid-state image sensor to the furthest position [mm]

Fl: Focal length of the objective optical system [mm]

Fno. : Effective F number of objective optical system

In addition, the endoscope apparatus which concerns on a 1st Example satisfy | fills the following conditions.

That is, the fixed-focus imaging unit which forms an image of an object with an objective optical system, and acquires an image signal by the solid-state imaging element by which the color filter is arrange | positioned for every pixel in the imaging plane vicinity of the objective optical system, and transfers from a solid-state imaging element. In an endoscope apparatus provided with a circuit system for processing a resulting image signal, the solid-state imaging device satisfies conditional expression (1), and the objective optical system satisfies conditional expression (2) and conditional expression (3), from the objective optical system to the object. It has a resolution of 35 µm or more when the distance is 4 mm, and a resolution of 0.45 mm or more when the distance from the objective optical system to the object is 50 mm.

Conditional Expression (1) 300 <IH / P <550

Conditional Expression (2) 300 <Fl / P <550

Conditional Expression (3) 2400 × P <Fno. <4200 × P

only,

P: horizontal pixel pitch [mm] of a solid-state image sensor

IH: distance from the center in the display area of the solid-state image sensor to the furthest position [mm]

Fl: Focal length of the objective optical system [mm]

Fno. : Effective F number of objective optical system

The endoscope end portion has a configuration as shown in FIGS. 10 and 11.

FIG. 10 is a front view of the endoscope insertion surface, and FIG. 11 is a cross-sectional view taken along line B-B in FIG.

The center of the treatment channel is located at a position 5.5 mm away from the optical axis of the imaging unit in the direction of the lower right 30 ° (lower left α = 30 ° in FIG. 10) toward the subject from the endoscope insertion surface. It is arranged. The angle of view θ in this direction is 59.2 °, and the beam height H of the first lens surface (the surface on the object side) of the objective optical system is 1.01 mm. You are in range. Accordingly, the endoscope apparatus according to the first embodiment thereby satisfies the following conditions.

That is, in an endoscope provided with a fixed focus imaging unit, the endoscope insertion section is further provided with a treatment instrument insertion channel, and passes through the treatment channel to a distance of 4 mm from the endoscope insertion portion to protrude the treatment instrument. When doing so, the imaging unit and the treatment instrument insertion channel are arranged so that at least a portion of the treatment instrument falls within the field of view of the imaging unit.

In the endoscope apparatus according to the first embodiment, the origin side of the depth of field is 60 mm, and the proximal side of the depth of field is 3.7 mm.

In the far field, it has sufficient performance for insertion into the body and screening of lesions. Moreover, the near point side has a resolution of 28 micrometers at 3.7 mm, and can enlarge and observe a colon pit pattern etc.

At this time, since the far side is continuously within the depth of field, the approach to the portion to be enlarged and observed can be smoothly performed. As a result, it is difficult to miss the subject.

In addition, since the operation of zooming such as an endoscope provided with a zoom imaging unit is unnecessary, the operation of the scope is easy.

Moreover, since there is no movable part in an imaging unit, compared with the endoscope provided with a zoom type imaging unit, an insertion part outer diameter is thin and manufacturing cost can also be suppressed low. In addition, since the treatment tool enters the field of view while observing the enlarged image, the treatment with high precision can be performed.

In addition, the first embodiment also satisfies the conditional expression (1) ', the conditional expression (2)', and the conditional expression (3) '.

Thus, the endoscope according to the first embodiment has a resolution of 28 m at an object distance of 3.7 mm, wherein the horizontal width of the display area of the solid-state image sensor is 2.4 mm and the horizontal direction of the image reflected on the monitor. If the width is 320 mm, the magnification on the monitor is 45 times, and the balance between the operating distance, resolution and magnification becomes very good, which is more suitable.

Second Embodiment

Solid-state image sensor of color with a color filter arranged for each pixel

IH = 1.676 mm P = 0.0035 mm IH / P = 479

Objective optical system

Fl = 1.58676 mm Fno. = 12.965 2ω = 162.6 °

Fl / P = 453 2400 × P = 8.4 4200 × P = 14.7

12 is a sectional view of the objective optical system of the second embodiment.

The second embodiment is an embodiment of an endoscope apparatus using a solid-state imaging device of color in which a color filter is arranged for each pixel.

MTF on the optical axis at spatial frequency 1 / (3 × P) at an object distance of 4 mm is 15.4%, and MTF on the optical axis at spatial frequency 1 / (3 × P} at an object distance of 50 mm is 13.9%. .

The range of the object side with a resolution of 25 / mm or more on the optical axis is 2.9 to 4.9 mm, and the range of the object side with a resolution of 2 / mm or more on the optical axis is 0 to 80 mm.

The resolution when the object distance is 4 mm is 32 µm and the resolution when the object distance is 50 mm is 0.34 mm.

Accordingly, the endoscope apparatus according to the second embodiment satisfies the following conditions.

That is, in an endoscope provided with a fixed focus imaging unit composed of an objective optical system and a solid-state imaging device of color in which color filters are arranged for each pixel, the solid-state imaging device satisfies conditional expression (1), and the objective optical system has a conditional expression ( 2) and conditional expression (3), MTF on the optical axis at spatial frequency 1 / (3 x P) at the object distance of 4 mm of the objective optical system, and spatial frequency 1 / (3 at the object distance of 50 mm The imaging surface of a solid-state image sensor is arrange | positioned in the position where all MTF on an optical axis in xP) becomes 10% or more.

Conditional Expression (1) 300 <IH / P <550

Conditional Expression (2) 300 <Fl / P <550

Conditional Expression (3) 2400 × P <Fno. <4200 × P

only,

P: horizontal pixel pitch [mm] of a solid-state image sensor

IH: distance from the center in the display area of the solid-state image sensor to the furthest position [mm]

Fl: Focal length of the objective optical system [mm]

Fno. : Effective F number of objective optical system

In addition, the endoscope apparatus which concerns on a 2nd Example meets the following conditions.

That is, in an endoscope apparatus including an endoscope including at least a fixed focus imaging unit and display means for displaying an image acquired by the imaging unit, in the imaging unit, a color filter is arranged for each pixel, and the conditional expression (1) is satisfied. And a range at the object side of the imaging unit having a resolution of 25 or more / mm at the center of the image displayed on the display means, comprising a solid-state imaging device configured to satisfy the conditional expressions (2) and (3). When the range at the object side of the imaging unit whose resolution is 2 or mm or more at the center of the image displayed on the display means is d2, the position of 3.5 mm from the most object side surface of the objective optical system constituting the imaging unit. The focal point on the optical axis at is contained in both d1 and d2, and the focal point at a position of 50 mm from the most object side surface of the objective optical system constituting the imaging unit is The imaging surface of a solid-state imaging element is arrange | positioned near the imaging position of an objective optical system so that only d2 may be included.

Conditional Expression (1) 300 <IH / P <550

Conditional Expression (2) 300 <Fl / P <550

Conditional Expression (3) 2400 × P <Fno. <4200 × P

only,

P: horizontal pixel pitch [mm] of a solid-state image sensor

IH: distance from the center in the display area of the solid-state image sensor to the furthest position [mm]

Fl: Focal length of the objective optical system [mm]

Fno. : Effective F number of objective optical system

In addition, the endoscope apparatus which concerns on a 2nd Example meets the following conditions.

That is, from an image pickup unit of a fixed focus type that forms an image of an object by an objective optical system and acquires an image signal by a solid-state image pickup device in which color filters are arranged for each pixel in the vicinity of the image plane of the objective optical system, and from the solid-state image pickup device. In an endoscope apparatus having a circuit system for processing a transferred image signal, the solid-state imaging device satisfies conditional expression (1), and the objective optical system satisfies conditional expression (2) and conditional expression (3), and the object from the objective optical system. It has a resolution of 35 µm or more when the distance to is 4 mm, and a resolution of 0.45 mm or more when the distance from the objective optical system to the object is 50 mm.

Conditional Expression (1) 300 <IH / P <550

Conditional Expression (2) 300 <Fl / P <550

Conditional Expression (3) 2400 × P <Fno. <4200 × P

only,

P: horizontal pixel pitch [mm] of a solid-state image sensor

IH: distance from the center in the display area of the solid-state image sensor to the furthest position [mm]

Fl: Focal length of the objective optical system [mm]

Fno. : Effective F number of objective optical system

The second embodiment is characterized by the fact that the viewing angle is 162.6 ° and a wide range can be observed at one time.

Therefore, when used as a medical endoscope, for example, it is suitable for the screening of lesions in order to have a wide field of view at a far field, and to obtain a resolution of 28 μm at 3.2 mm. Possible endoscope devices can be constructed.

Third Embodiment

Solid-state image sensor of color with a color filter arranged for each pixel

IH = 1.3 mm P = 0.0025 mm IH / P = 520

Objective optical system

Fl = 1.33785 mm Fno. = 10.003 2ω = 132.1 °

Fl / P = 535 2400 × P = 6.0 4200 × P = 10.5

Fig. 13 is a sectional view of the objective optical system of the third embodiment.

The third embodiment is an embodiment of an endoscope apparatus using a solid-state imaging device of color in which color filters are arranged for each pixel.

The MTF on the optical axis at the spatial frequency 1 / (3 × P) at an object distance of 4 mm is 9.2%, and the MTF on the optical axis at the spatial frequency 1 / (3 × P) at an object distance of 50 mm is 10.6%. .

The range of the object side with a resolution of 25 / mm or more on the optical axis is 3.7 to 6.0 mm, and the range of the object side with a resolution of 2 / mm or more on the optical axis is 0 to 85 mm.

The resolution when the object distance is 4 mm is 30 µm and the resolution when the object distance is 50 mm is 0.28 mm.

Accordingly, the endoscope apparatus according to the third embodiment satisfies the following conditions.

That is, the fixed-focus imaging unit which forms an image of an object with an objective optical system, and acquires an image signal by the solid-state imaging element by which the color filter is arrange | positioned for every pixel in the imaging plane vicinity of the objective optical system, and transfers from a solid-state imaging element. In an endoscope apparatus provided with a circuit system for processing a resulting image signal, the solid-state imaging device satisfies conditional expression (1), and the objective optical system satisfies conditional expression (2) and conditional expression (3), from the objective optical system to the object. It has a resolution of 35 µm or more when the distance is 4 mm, and a resolution of 0.45 mm or more when the distance from the objective optical system to the object is 50 mm.

Conditional Expression (1) 300 <IH / P <550

Conditional Expression (2) 300 <Fl / P <550

Conditional Expression (3) 2400 × P <Fno. <4200 × P

only,

P: horizontal pixel pitch [mm] of a solid-state image sensor

IH: distance from the center to the furthest position in the display area of the solid-state image sensor [mm]

Fl: Focal length of the objective optical system [mm]

Fno. : Effective F number of objective optical system

The third embodiment is an example in which the parameters of IH / P, Fl / P, and Fno. Are close to the upper limits within the ranges defined by the above conditional expressions (1), (2), and (3).

In the endoscope apparatus according to the third embodiment, the depth of field on the proximal side becomes 4.2 mm, making it difficult to approach a little, but a resolution of 27 m is obtained at 4.2 mm, and the object of the present invention can be sufficiently satisfied. Moreover, since the number of pixels of a solid-state image sensor is comparatively large, it has the characteristic that a high precision image is obtained.

[Example 4]

Solid-state image sensor of color with a color filter arranged for each pixel

IH = 1.32 mm P = 0.004 mm IH / P = 330

Objective optical system

Fl = 1.27394 mm Fno. = 10.326 2ω = 125.9 °

Fl / P = 318 2400 × P = 9.6 4200 × P = 16.8

Fig. 14 is a sectional view of the objective optical system of the fourth embodiment.

The fourth embodiment is an embodiment of an endoscope apparatus using a solid-state imaging device of color in which a color filter is arranged for each pixel.

The MTF on the optical axis at the spatial frequency 1 / (3 × circle) at an object distance of 4 mm is 24.8%, and the MTF on the optical axis at the spatial frequency at 1 / (3 × P) at an object distance of 50 mm is 11.5%.

The range of the object side with a resolution of 25 / mm or more on the optical axis is 3.2 to 3.9 mm, and the range of the object side with a resolution of 2 / mm or more on the optical axis is 0 to 55 mm.

The resolution when the object distance is 4 mm is 38 µm and the resolution when the object distance is 50 mm is 0.47 mm.

Therefore, the endoscope apparatus which concerns on 4th Example satisfy | fills the following conditions.

That is, in an endoscope provided with a fixed focus imaging unit composed of an objective optical system and a solid-state imaging device of color in which color filters are arranged for each pixel, the solid-state imaging device satisfies conditional expression (1), and the objective optical system has a conditional expression ( 2) and conditional expression (3), MTF on the optical axis at spatial frequency 1 / (3 x P) at the object distance of 4 mm of the objective optical system, and spatial frequency 1 / (3 at the object distance of 50 mm The imaging surface of a solid-state image sensor is arrange | positioned in the position where all MTF on an optical axis in xP) becomes 10% or more.

Conditional Expression (1) 300 <IH / P <550

Conditional Expression (2) 300 <Fl / P <550

Conditional Expression (3) 2400 × P <Fno. <4200 × P

only,

P: horizontal pixel pitch [mm] of a solid-state image sensor

IH: distance from the center in the display area of the solid-state image sensor to the furthest position [mm]

Fl: Focal length of the objective optical system [mm]

Fno. : Effective F number of objective optical system

In addition, the endoscope apparatus which concerns on 4th Example satisfy | fills the following conditions.

That is, in an endoscope apparatus including an endoscope including at least a fixed focus imaging unit and display means for displaying an image acquired by the imaging unit, in the imaging unit, a color filter is arranged for each pixel, and the conditional expression (1) is satisfied. And an objective optical system satisfying Conditional Expression (2) and Conditional Expression (3), wherein the resolution at the center of the image displayed on the display means is at least 25 / mm at the object side of the imaging unit. When d1 is a range on the object side of the imaging unit whose resolution at the center of the image displayed on the display means is 2 / mm or more, d2, it is 3.5 mm from the most object side surface of the objective optical system constituting the imaging unit. The object point on the optical axis at the position is included in both d1 and d2, and the object point is located at a position of 50 mm from the most object side surface of the objective optical system constituting the imaging unit. To include only d2, it is the imaging surface of the solid-state image sensor arranged near the imaging position of the objective optical system.

Conditional Expression (1) 300 <IH / P <550

Conditional Expression (2) 300 <Fl / P <550

Conditional Expression (3) 2400 × P <Fno. <4200 × P

only,

P: horizontal pixel pitch [mm] of a solid-state image sensor

IH: distance from the center in the display area of the solid-state image sensor to the furthest position [mm]

Fl: Focal length of the objective optical system [mm]

Fno. : Effective F number of objective optical system

The fourth embodiment is an example in which each parameter of IH / P, Fl / P, and Fno. Is close to the lower limit within the range specified by the above conditional expression (1), conditional expression (2) and conditional expression (3).

In the endoscope apparatus according to the fourth embodiment, a resolution of 32 占 퐉 is obtained at 3.3 mm.

Although the resolution decreases slightly compared with the above-mentioned condition (1) ', condition (2)' and condition (3) ', the object of the present invention can be sufficiently satisfied.

In addition, since the number of pixels of the solid-state imaging device is relatively small, it is advantageous in that the external diameter of the endoscope insertion portion is reduced in size, the tip length in hardened length, and the like are easily performed.

[Example 5]

Solid-state imaging device in which a luminance signal is generated for each pixel

IH = 1.05 mm F = 0.0035 mm IH / P = 300

Objective optical system

Fl = 1.04272 mm Fno. = 8.625 2ω = 133.7 °

Fl / P = 298 1600 × P = 5.6 2800 × P = 9.8

Fig. 15 is a sectional view of the objective optical system of the fifth embodiment.

The fifth embodiment is an embodiment of an endoscope apparatus using a solid-state imaging device in which a luminance signal is generated for each pixel.

The MTF on the optical axis at the spatial frequency 1 / (2 x P) at an object distance of 4 mm is 14.3%, and the MTF on the optical axis at the spatial frequency 1 / (2 x P) at an object distance of 50 mm is 11.6%. .

The range of the object side with the resolution of 25 / mm or more on the optical axis is 3.2-5.5 mm, and the range of the object side with the resolution of 2 / mm or more on the optical axis is 0-80 mm.

The resolution when the object distance is 4 mm is 29 µm and the resolution when the object distance is 50 mm is 0.34 mm.

Therefore, the endoscope apparatus which concerns on 5th Example satisfy | fills the following conditions.

That is, in an endoscope having a fixed-focus imaging unit composed of an objective optical system and a solid-state imaging device for generating luminance signals for each pixel, the solid-state imaging device satisfies conditional expression (4), and the objective optical system is conditional expression (5). ) And conditional expression (6), MTF on the optical axis at the spatial frequency 1 / (2 x P) at the object distance of 4 mm of the objective optical system, and the spatial frequency at 1 / (2 x at the object distance of 50 mm The imaging surface of a solid-state image sensor is arrange | positioned in the position where all MTF on the optical axis in P) becomes 10% or more.

Conditional Expression (4) 200 <IH / P <360

Conditional Expression (5) 200 <Fl / P <360

Conditional Expression (6) 1600 × P <Fno. <2800 × P

only,

P: horizontal pixel pitch [mm] of a solid-state image sensor

IH: distance from the center in the display area of the solid-state image sensor to the furthest position [mm]

Fl: Focal length of the objective optical system [mm]

Fno. : Effective F number of objective optical system

In addition, the endoscope apparatus which concerns on 5th Example satisfy | fills the following conditions.

That is, in an endoscope apparatus including an endoscope including at least a fixed-focus imaging unit, and display means for displaying an image acquired by the imaging unit, the imaging unit generates a luminance signal for each pixel, and further includes conditional expression (4). And a solid-state imaging device that satisfies the above condition, and an objective optical system that satisfies the conditional expressions (5) and (6), wherein the resolution at the center of the image displayed on the display means is 25 / mm or more in the object side of the imaging unit. Is d1 and the range on the object side of the imaging unit whose resolution at the center of the image displayed on the display means is 2 / mm or more is d2, the distance of 3.5 mm from the surface of the object side of the objective optical system constituting the imaging unit. The object point on the optical axis at the position is included in both d1 and d2, and the object point is located at a position of 50 mm from the most object side surface of the objective optical system constituting the imaging unit. To include only d2, there is an image pickup surface of said solid state image pickup device is arranged near the imaging position of the objective optical system.

Conditional Expression (4) 200 <IH / P <360

Conditional Expression (5) 200 <Fl / P <360

Conditional Expression (6) 1600 × P <Fno. <2800 × P

only,

P: horizontal pixel pitch [mm] of a solid-state image sensor

IH: distance from the center in the display area of the solid-state image sensor to the furthest position [mm]

Fl: Focal length of the objective optical system [mm]

Fno. : Effective F number of objective optical system

In addition, the endoscope apparatus which concerns on 5th Example satisfy | fills the following conditions.

That is, from the fixed focus type imaging unit which forms an image of an object with an objective optical system, and acquires an image signal by the solid-state imaging element which produces | generates a luminance signal for each pixel in the vicinity of the imaging surface of the objective optical system, and from a solid-state imaging element. In an endoscope apparatus having a circuit system for processing a conveyed image signal, the solid-state imaging device satisfies conditional expression (4), and the objective optical system satisfies conditional expression (5) and conditional expression (6), and the object from the objective optical system. It has a resolution of 35 µm or more when the distance to is 4 mm, and a resolution of 0.45 mm or more when the distance from the objective optical system to the object is 50 mm.

Conditional Expression (4) 200 <IH / P <360

Conditional Expression (5) 200 <Fl / P <360

Conditional Expression (6) 1600 × P <Fno. <2800 × P

only,

P: horizontal pixel pitch [mm] of a solid-state image sensor

IH: distance from the center in the display area of the solid-state image sensor to the furthest position [mm]

Fl: Focal length of the objective optical system [mm]

Fno. : Effective F number of objective optical system

Since the endoscope apparatus according to the fifth embodiment uses a solid-state imaging device that generates a luminance signal for each pixel, it is easy to devise an illuminating light or a filter in an objective optical system to easily observe fluorescence, infrared light, narrowband light, or the like. It can be used for special light observation.

In addition, since the endoscope apparatus according to the fifth embodiment uses a solid-state imaging element in which a luminance signal is generated for each pixel, the number of pixels is small compared with an endoscope using a color solid-state imaging element in which a color filter is arranged for each pixel. The imaging unit of the same specification can be configured. Therefore, it is advantageous in that the external diameter of the endoscope insertion portion can be reduced in size, the tip length can be shortened, and the like.

Also, as shown in Fig. 18, there is a solid-state imaging device having a structure in which the position of the pixel is shifted by PH / 2 with respect to the pixel pitch PH in the horizontal direction for every one line in the horizontal direction of the pixel array. In the case of such a solid-state image pickup device, the conventional solid-state image pickup device in which pixels are arranged horizontally and horizontally differs in the method of generating a luminance signal, and the resolution in the output image signal is a conventional solid-state image pickup device in which pixels are arranged horizontally and horizontally. The report is equivalent to 1.6 times the number of pixels (Japanese Photographic Journal 63 (3), 1-5 (2000)).

Therefore, when the pixel pitch in the oblique direction is set to P 'in Fig. 18, it can be applied to the endoscope and endoscope apparatus of the present invention by converting the pixel pitch P in the horizontal direction by the following formula.

P = P '×

Next, a so-called three-plate type imaging unit of a system in which three solid-state imaging elements are used to generate one image signal is considered.

In the three-plate type, light from a subject can be divided into three by a prism, and is allocated to the solid-state image sensor corresponding to each of three primary colors of R, G, and B. In each individual imaging device, a luminance signal of a corresponding color is generated for each pixel. Then, one luminance signal and one color information are obtained from three of the luminance signal of R, the luminance signal of G, and the luminance signal of B. At this time, the values of IH / P, Fl / P, and Fno. Are the same in all three solid-state imaging elements.

Therefore, in the case of the three-plate type, the same can be applied to the endoscope and the endoscope apparatus of the present invention in the same manner as in the case of the solid-state imaging device in which the luminance signal is generated for each pixel.

Claims (8)

In the endoscope provided with the objective optical system and the fixed-focus imaging unit comprised with the solid-state image sensor of the color in which the color filter was arrange | positioned for every pixel, The solid-state imaging device satisfies the conditional formula (1), The objective optical system satisfies conditional formula (2) and conditional formula (3), MTF (Modulation Transfer Function) on the optical axis at the spatial frequency 1 / (3 x P) at the object distance 4 mm of the objective optical system, and at the spatial frequency 1 / (3 x P) at the object distance 50 mm. An endoscope provided with a fixed-focus imaging unit, wherein the imaging plane of the solid-state imaging device is disposed at a position where all of the MTF (Modulation Transfer Function) on the optical axis are 10% or more. Conditional Expression (1) 300 <IH / P <550 Conditional Expression (2) 300 <Fl / P <550 Conditional Expression (3) 2400 × P <Fno. <4200 × P only, P: horizontal pixel pitch [mm] of a solid-state image sensor IH: distance from the center in the display area of the solid-state image sensor to the furthest position [mm] Fl: Focal length of the objective optical system [mm] Fno. : Effective F number of objective optical system An endoscope apparatus including an endoscope including a fixed focus imaging unit, and display means for displaying an image acquired by the imaging unit, The image pickup unit is composed of a solid-state image pickup device in which a color filter is disposed for each pixel and satisfies conditional expression (1), and an objective optical system that satisfies conditional expression (2) and conditional expression (3), and is displayed on the display means. The range at the object side of the imaging unit whose resolution at the center of is 25 or more is d1, and the range at the object side of the imaging unit having the resolution at the center of the image displayed on the display means is 2 / mm or more at d2. In this case, the object point on the optical axis at a position of 3.5 mm from the plane of the object side of the objective optical system constituting the imaging unit is included in both d1 and d2, and the object side of the objective optical system constituting the imaging unit is included. The imaging surface of the solid-state imaging device is arranged with respect to the objective optical system so that the object point located 50 mm from the surface is included only in d2. Endoscopic devices. Conditional Expression (1) 300 <IH / P <550 Conditional Expression (2) 300 <Fl / P <550 Conditional Expression (3) 2400 × P <Fno. <4200 × P only, P: horizontal pixel pitch [mm] of a solid-state image sensor IH: distance from the center in the display area of the solid-state image sensor to the furthest position [mm] Fl: Focal length of the objective optical system [mm] Fno. : Effective F number of objective optical system A fixed-focus imaging unit that forms an image of an object by an objective optical system and acquires an image signal by a solid-state imaging device in which color filters are arranged for each pixel, and a circuit for processing the image signal transferred from the solid-state imaging device. In the endoscope device provided with a system, The solid-state imaging device satisfies the conditional formula (1), The objective optical system satisfies conditional formula (2) and conditional formula (3), An endoscope apparatus having a resolution of 35 µm or more when the distance from the objective optical system to an object is 4 mm, and a resolution of 0.45 mm or more when the distance from the objective optical system to an object is 50 mm. Conditional Expression (1) 300 <IH / P <550 Conditional Expression (2) 300 <Fl / P <550 Conditional Expression (3) 2400 × P <Fno. <4200 × P only, P: horizontal pixel pitch [mm] of a solid-state image sensor IH: distance from the center in the display area of the solid-state image sensor to the furthest position [mm] Fl: Focal length of the objective optical system [mm] Fno. : Effective F number of objective optical system In an endoscope provided with an objective optical system and a fixed focus imaging unit composed of a solid-state imaging device for generating a luminance signal for each pixel, The solid-state imaging device satisfies the conditional formula (4), The objective optical system satisfies conditional formula (5) and conditional formula (6), MTF (Modulation Transfer Function) on the optical axis at the spatial frequency 1 / (2 × P) at the object distance 4 mm of the objective optical system, and at the spatial frequency 1 / (2 × P) at the object distance 50 mm. An endoscope provided with a fixed-focus imaging unit, wherein the imaging plane of the solid-state imaging device is disposed at a position where the MTF (Modulation Transfer Function) on the optical axis becomes 10% or more. Conditional Expression (4) 200 <IH / P <360 Conditional Expression (5) 200 <Fl / P <360 Conditional Expression (6) 1600 × P <Fno. <2800 × P only, P: horizontal pixel pitch [mm] of a solid-state image sensor IH: distance from the center in the display area of the solid-state image sensor to the furthest position [mm] Fl: Focal length of the objective optical system [mm] Fno. : Effective F number of objective optical system An endoscope apparatus including an endoscope including a fixed focus imaging unit, and display means for displaying an image acquired by the imaging unit, The imaging unit is composed of a solid-state imaging element for generating a luminance signal for each pixel and satisfying the conditional expression (4), and an objective optical system satisfying the conditional expressions (5) and (6), and displayed on the display means. The range at the object side of the imaging unit whose resolution at the center of the image is 25 / mm or more is d1, and the range at the object side of the imaging unit whose resolution at the center of the image displayed by the display means is 2 / mm or more d2. In this case, the object point on the optical axis at a position of 3.5 mm from the plane of the object side of the objective optical system constituting the imaging unit is included in both d1 and d2, and the object side of the objective optical system constituting the imaging unit is included. The imaging surface of the solid-state imaging device is arranged with respect to the objective optical system so that the object point at a position of 50 mm from the surface of is included only in d2. The endoscope apparatus. Conditional Expression (4) 200 <IH / P <360 Conditional Expression (5) 200 <Fl / P <360 Conditional Expression (6) 1600 × P <Fno. <2800 × P only, P: horizontal pixel pitch [mm] of a solid-state image sensor IH: distance from the center in the display area of the solid-state image sensor to the furthest position [mm] Fl: Focal length of the objective optical system [mm] Fno. : Effective F number of objective optical system A fixed-focus imaging unit for forming an image of an object by an objective optical system and acquiring an image signal by a solid-state imaging device for generating a luminance signal for each pixel, and processing the image signal transferred from the solid-state imaging device. In an endoscope device provided with a circuit system, The solid-state imaging device satisfies the conditional formula (4), The objective optical system satisfies conditional formula (5) and conditional formula (6), An endoscope apparatus having a resolution of 35 µm or more when the distance from the objective optical system to an object is 4 mm, and a resolution of 0.45 mm or more when the distance from the objective optical system to an object is 50 mm. Conditional Expression (4) 200 <IH / P <360 Conditional Expression (5) 200 <Fl / P <360 Conditional Expression (6) 1600 × P <Fno. <2800 × P only, P: horizontal pixel pitch [mm] of a solid-state image sensor IH: distance from the center in the display area of the solid-state image sensor to the furthest position [mm] Fl: Focal length of the objective optical system [mm] Fno. : Effective F number of objective optical system In the endoscope provided with the fixed-focus imaging unit of any one of Claims 1-4, The endoscope insertion portion further includes a treatment instrument insertion channel, so that at least a portion of the treatment instrument enters the field of view of the imaging unit when the treatment instrument is protruded through the treatment channel up to a distance of 4 mm from the endoscope insertion portion. And the imaging unit and the treatment instrument insertion channel are arranged. The method according to any one of claims 2, 3, 5 or 6, The endoscope insertion portion further includes a treatment instrument insertion channel, so that at least a portion of the treatment instrument enters the field of view of the imaging unit when the treatment instrument is protruded through the treatment channel up to a distance of 4 mm from the endoscope insertion portion. And the imaging unit and the treatment instrument insertion channel are arranged.

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