JP4402491B2 - Enlarged video module and manufacturing method thereof - Google Patents

Description

The present invention relates to expanded video module for observation inside a living body, in particular to a method for producing a magnified video module and the enlarged video module having an enlargement magnification suitable for cell observation.

The conventional endoscope has a wide viewing angle of about 90 ° to 140 ° so that the tissue inside the living body can be observed and examined without overlooking the lesioned part. This conventional endoscope changes the distance to the subject and obtains a magnified image and a reduced image of the observation target. For example, a range of 3 mm to 50 mm can be observed without adjusting the focus, and a deep object with a fixed focus can be observed. Has depth of field.
Further, the image display magnification of a conventional endoscope is approximately 30 to 50 times on a 14-inch size monitor screen, and has a magnification sufficient for observing a diseased tissue.

A zoom optical system is used for further enlarging observation of a diseased tissue in such a conventional endoscope.
The maximum magnification of the zoom optical system is approximately 70 times on a 14-inch monitor screen.
However, since the zoom optical system needs to have a built-in zoom operation unit, the outer diameter of the distal end insertion portion of the endoscope becomes a large diameter of 10 mm or more, and the operation at the time of endoscope observation becomes complicated. . For this reason, the application of the zoom optical system in the endoscope is limited.

By the way, cytodiagnosis is performed when it is difficult to determine the presence or absence of abnormality from the findings of tissue images such as very small lesions.
Cytodiagnosis is an examination technique in which a tissue suspected of being abnormal in endoscopic observation is collected using a treatment tool and taken out of the body, and then examined for abnormality at the cellular level by microscopic observation.

In these observations, in the endoscopic observation, an illumination optical system is arranged around the objective optical system to perform oblique illumination, whereas in the microscopic observation, the objective optical system and the illumination optical system are sandwiched between the specimens. Observation is performed by transmitting the specimen from the back side with the specimen arranged oppositely.
In microscopic observation, the specimen is processed in advance to a state suitable for observation. For example, a treatment such as thinly slicing so as to easily transmit light, or adding contrast by staining is performed.

Conventionally, a laser scanning confocal endoscope has been proposed as one that can be inserted into a living body and has a resolution necessary for cell observation.
In general, a confocal optical system has a pinhole on the image side, which is about the size of an air disk, and is configured to acquire information about the diffraction limit for each point from a subject in the field of view. Laser light is scanned by the light projecting optical system, and information about each point obtained from the reflected light from the subject is synthesized to construct information about the plane and the solid as an image.
Further, the laser scanning confocal endoscope has a high resolution not only in the lateral direction in the plane but also in the depth direction.

By the way, a conventional endoscope that requires a wide field of view has an imaging unit including an objective optical system and an imaging element having an imaging magnification smaller than 1, and reduces an object to form an image on an imaging surface. It has become.
In other words, the conventional endoscope realizes a deep depth of field because the focal depth on the image plane side is enlarged and projected on the subject side by the objective optical system.
In addition, the conventional endoscope performs adjustment to fix the imaging surface of the imaging element near the image plane of the objective optical system when the imaging unit is assembled so that a depth of field suitable for observation can be obtained.

An example of a conventional endoscope focus adjustment method will be described with reference to FIG.
In a conventional endoscope objective optical system, the change in the relative position between the subject and the object-side tip surface of the objective optical system is reduced and projected onto the image side through the objective optical system. It becomes difficult to detect.
For this reason, the upper limit ZoA and lower limit ZoB of the desired depth of field, for example, a distance of 50 mm and 3 mm from the object-side tip surface of the objective optical system, and the subject is connected to the imaging surface of the image sensor through the objective optical system. Evaluate the resolution of multiple images ZmA, ZmB. Then, focus adjustment is performed by obtaining a position where the resolution of the plurality of images ZmA and ZmB is in an optimal balance and moving the imaging surface of the imaging element in the optical axis direction of the objective optical system.

  Further, in the conventional objective optical system of an endoscope, even when the subject is tilted with respect to the objective optical system, the subject is reduced and imaged on the imaging surface of the imaging device. The imaging state is not significantly asymmetrical around the field of view, and the resolution balance of the photographed image does not deteriorate. Therefore, in the conventional focus adjustment of the photographing unit of the endoscope, it is possible to obtain a good image only by guaranteeing the inclination of the subject by the mechanical accuracy of the focus adjustment device.

On the other hand, the microscope has an objective optical system having an imaging magnification larger than 1, and enlarges the subject to form an image on the image plane.
In other words, the microscope projects a reduced depth of focus on the image plane side on the subject side, and has a shallow depth of field.
For this reason, the microscope is configured to be in focus by moving the stage position for fixing the subject.

  In an objective optical system having an imaging magnification greater than 1, the change in the relative position between the subject and the object-side tip surface of the objective optical system is enlarged and projected to the image side through the objective optical system. When the imaging surface of the image sensor is placed on the imaging surface, the imaging state on the imaging surface when the subject is tilted with respect to the objective optical system becomes significantly asymmetrical around the field of view, resulting in a resolution balance of the captured image. It will have a bad effect. For this reason, the microscope stage for fixing the subject is precisely adjusted so that it does not tilt with respect to the objective optical system during assembly.

In the conventional observation method in which a living tissue is taken out of the body and diagnosed using these observation apparatuses, it takes several days to several weeks to determine whether or not the tissue is abnormal.
In addition, the cell specimen to be observed is a specimen obtained by separating and fixing a small part of the collected tissue. Therefore, although information as a cell structure can be obtained simply, it is significantly different from the environment in the living body, so that it is not possible to obtain functional information including, for example, the reflux state of the body fluid filling the cells.
For this reason, it is required to enable real-time observation of cells inside a living body with an endoscope.

In order to image a disease inside a living body at a cellular level, a small video module including an objective optical system having a high imaging magnification and high resolution comparable to a microscope is required.
However, conventional endoscope objective optical systems do not satisfy the required specifications.
On the other hand, a microscope has a performance for imaging at a cell level, but is large and cannot be introduced into a living body.
Therefore, no video module that satisfies the above requirements has been proposed at present.

  Laser scanning confocal endoscopes have a problem in scanning speed, and have not yet achieved real-time observation in vivo.

  Further, when observing the inside of a living body, it is impossible to move and fix the subject with high precision to a position where the objective optical system is in focus so as to observe the collected specimen with a microscope. Therefore, in the video module, it is necessary to adjust and fix in advance the position of the imaging surface of the imaging device at the optimum focus position for observing the living body in the living body.

However, when the focus adjustment of the video module is performed by the focus adjustment method used in a conventional endoscope, the following problems have been encountered.
1) The depth of field of the objective optical system is very narrow, and the change in the relative position between the subject and the object-side tip surface of the objective optical system is enlarged and projected to the image side through the objective optical system. Therefore, it is necessary to place subjects at a plurality of positions within the depth of field, and the focus adjustment work cannot be stably reproduced.
2) Even if the subject is slightly inclined with respect to the objective optical system within the mechanical accuracy of the focus adjustment device, the image formation state on the image pickup surface of the image pickup device becomes extremely asymmetric around the field of view, and the solution of the photographed image is reduced. This will adversely affect the image balance.
3) In an objective optical system having a specification for observing the object-side tip surface of the objective optical system in contact with the subject, the subject is placed because the near point of the depth of field is inside the objective optical system. I can't.

The present invention has been made in view of the above problems, and an object thereof is to provide an enlarged video module capable of observing cells inside a living body in real time and a method of manufacturing the enlarged video module.

To achieve the above object, enlarged video module according to the present invention, Oite expanding video module the imaging magnification with a greater than one objective optical system and the imaging device, the objective optical system comprises, in order from the object side The front group having a positive focal length and an aperture stop are included, and the following conditional expression is satisfied .
0.9 ≦ | coswy ′ / coswy | ≦ 1.1
0.2 ≦ φ1 / φ2 / f1 ≦ 2
Where wy ′ is the incident angle of the principal ray corresponding to the maximum viewing angle in the magnified video module to the imaging surface of the imaging device, wy is the half viewing angle, φ1 is the aperture diameter of the aperture stop, and φ2 is the objective. The maximum outer diameter of the optical system, f1, is the focal length of the front group.

In order to achieve the above object, enlarged video module according to the present invention, Oite expanding video module the imaging magnification with a greater than one objective optical system and the imaging device, to satisfy the following condition: It is characterized by.
0.1 ≦ | p × (NA) ² /(0.61×λ×βo)|≦0.8
Here, p is the pixel size of the imaging device, NA is the object-side numerical aperture of the objective optical system, λ is the e-line wavelength 0.546 [μm], and βo is the magnification of the objective optical system.

According to another aspect of the present invention, there is provided a method of manufacturing an enlarged video module, the step of fixing the position of a subject at a predetermined distance with respect to an object-side tip surface of the objective optical system , A step of moving the element to detect two positions of the image sensor where the image of the subject has a predetermined contrast, and a step of obtaining a position of the image sensor from which the contrast of the image of the object is maximized from the two detected positions The focus position is adjusted through the steps .

Also, in the method for manufacturing an enlarged video module according to the present invention, any one of the above-mentioned enlarged video modules is brought into contact with the object-side front end surface of the objective optical system, and the position of the subject so as to have a predetermined contrast. The focus range is confirmed through a step of moving the lens in the direction of the optical axis of the objective optical system and a step of detecting the position of the subject having a predetermined contrast .

Prior to the description of the embodiments, the effects of the present invention will be described.
First, as the objective optical system of the magnifying video module of the present invention, an objective optical system of a magnifying endoscope that realizes the small size, high magnification, and high resolution necessary for in vivo cell observation will be described. Further, as an example of the application of the magnifying video module of the present invention, a case where a magnifying endoscope is used in combination with a conventional endoscope is described.

In order to examine a diseased tissue without overlooking it within a wide body cavity, observation is performed with a conventional endoscope having a wide field of view.
On the other hand, for sites that are difficult to judge from tissue images such as micro-lesions, the magnified video module of the present invention is used as a magnifying endoscope, and is introduced into the body through a treatment instrument insertion channel of a conventional endoscope. Perform observations at the cellular level.
The tissue image observed with a conventional endoscope reflects information on the parenchyma located deeper than the epithelial cells, and exhibits a warm hue. On the other hand, epithelial cells observed with a magnifying endoscope are transparent and have low contrast, and are difficult to see because light is transmitted through observation with a conventional endoscope.

Therefore, when observing a cell in a magnified manner, a pigment dispersion is performed in advance as necessary. By spraying the pigment, it is possible to add contrast to the subject by using the difference in time during which the nucleus or wall in the cell discharges the pigment.
After spraying the pigment, while observing with a conventional endoscope, the magnifying endoscope of the present invention is guided to a site where magnifying observation is desired, and its tip is brought into close contact with the subject and fixed.
In addition, the tissue image observed through the conventional endoscope and the cell image observed through the magnifying endoscope are simultaneously displayed on the TV monitor.

  Here, in order to enable cell observation in a living body, the objective optical system constituting the magnified video module of the present invention needs to satisfy requirements such as high magnification, high resolution, and small size.

First, the magnification necessary for visualizing the fine structure of the cell in the objective optical system constituting the enlarged video module of the present invention will be described.
If the observation magnification on the TV monitor is βm, the following equation is given.
βm = βo × βd
Here, βo is the magnification of the objective optical system, and is the magnification at which the subject is imaged on the image sensor. βd is a display magnification, which is obtained by dividing the monitor display screen size by the display screen size of the image sensor.

As described above, the observation magnification on a 14-inch monitor that can be realized by a conventional endoscope is about 30 to 50 times, while the observation magnification of a zoom optical system having an enlargement function is about 70 times. is there.
For cell observation, an observation magnification of about 200 to 2000 times is required on a 14-inch monitor.
Therefore, it is desirable that the objective optical system in the enlarged video module of the present invention satisfies the following conditional expressions (4) and (1).
1 <| βo | ≦ 10 (4)
0.9 ≦ | coswy ′ / coswy | ≦ 1.1 (1)
Here, βo is the magnification of the objective optical system, wy ′ is the incident angle of the principal ray corresponding to the maximum viewing angle in the enlarged video module, and wy is the half viewing angle.
If the lower limit of conditional expression (1) is not reached, the incident angle to the image sensor becomes large, and uniformity of image quality such as color reproducibility and brightness cannot be maintained in the field of view.
On the other hand, if the upper limit of conditional expression (1) is exceeded, the viewing angle becomes large and the required magnification cannot be secured.

Next, the resolution of the objective optical system constituting the enlarged video module of the present invention will be described.
Although the diseased tissue can be identified with a resolution on the order of millimeters or submillimeters, when observing cells, a resolution in units of microns or submicrons is required.
Further, in order to image fine information of a subject that is transparent and has a small difference in refractive index and low contrast, it is necessary to enhance the contrast using interference of diffracted light from the subject.
Therefore, the objective optical system in the magnified video module of the present invention needs to increase the object-side numerical aperture NA so that high-order diffracted light can be taken in, and satisfies the following conditional expression (5): Is desirable.
0.1 ≦ NA ≦ 0.8 (5)
Furthermore, in order to achieve both high contrast and image definition, the resolution of the objective optical system must be set higher than the resolution determined by the pitch of the image sensor and lower than the resolution determined by the diffraction limit. ) Is desirable.
0.1 ≦ | p × (NA) ² /(0.61×λ×βo)|≦0.8 (3)
Here, p is the pixel size of the image sensor provided in the enlargement video module, NA is the object-side numerical aperture of the objective optical system, λ is the e-line wavelength 0.546 [μm], and βo is the magnification of the objective optical system.
If the lower limit of conditional expression (3) is not reached, sufficient contrast cannot be obtained.
On the other hand, if the upper limit of conditional expression (3) is exceeded, aberration correction becomes difficult and a fine image cannot be obtained.

Furthermore, the downsizing of the objective optical system constituting the enlarged video module of the present invention will be described.
In order to allow the magnifying endoscope of the present invention to pass through a channel for inserting a treatment tool of a conventional endoscope or the like, it is desirable that the outer diameter of the magnifying endoscope is φ4 or less. Accordingly, it is desirable to reduce the outer diameter of the objective optical system to about φ2 mm or less.

In this way, a further compact objective optical system having a high imaging magnification and a high resolution includes, in order from the object side, a lens group having a positive focal length, and an aperture stop. It is desirable to satisfy (2).
0.2 ≦ φ1 / φ2 / f1 ≦ 2 (2)
Where φ1 is the aperture diameter of the aperture stop, φ2 is the maximum outer diameter of the objective optical system, and f1 is the focal length of the lens group having the positive focal length. This conditional expression is a condition for achieving miniaturization while avoiding a large aperture of the objective optical system due to high NA.
If the lower limit of conditional expression (2) is not reached, the overall length and outer diameter will increase, making it difficult to reduce the size of the objective optical system.
On the other hand, if the upper limit of conditional expression (2) is exceeded, aberration correction becomes difficult.

Further, in the enlarged video module of the present invention, in order to obtain a field of view without distortion to the periphery, the objective optical system is sequentially arranged from the object side, the front group having a positive focal length, an aperture stop, and a positive focal length. It is desirable to comprise from the rear group which has.
At this time, it is desirable that the following conditional expression (6) is satisfied in order to achieve both miniaturization and high magnification.
2 ≦ f2 / f1 ≦ 10 (6)
Here, f1 is the focal length of the front group, and f2 is the focal length of the rear group.
If the lower limit of conditional expression (2) is not reached, the necessary magnification cannot be secured.
On the other hand, if the upper limit of conditional expression (2) is exceeded, the overall length and outer diameter will increase, making it difficult to reduce the size.

  The method for adjusting the focus position of the enlarged video module according to the present invention preferably includes the step of setting the distance at which the subject is arranged by measuring the amount of movement of the subject in submicron units.

  In addition, according to the method of adjusting the focus position of the enlarged video module according to the present invention, the distance at which the subject is placed by placing a member manufactured with submicron accuracy in contact between the object-side tip of the objective optical system and the subject. Preferably, a step of setting is included.

  Further, the focus position adjustment method of the enlarged video module according to the present invention detects the posture of the subject using the interference fringes generated between the object-side front end surface of the objective optical system and the subject, and adjusts the subject when the focus is adjusted. Preferably, the method includes a step of determining a reference position.

Hereinafter, the present invention will be described with reference to the drawings.
First, an embodiment of the enlarged video module of the present invention will be described.
First Embodiment FIGS. 1A and 1B are diagrams showing an optical configuration of a first embodiment of an enlarged video module according to the present invention. FIG. 1A is a cross-sectional view, and FIG. 1B is a cross-sectional view as viewed from the direction of arrow A in FIG. is there.
As shown in FIG. 1A, the enlarged video module according to the first embodiment includes an objective unit including an objective lens group 21 having the same outer diameter with respect to the objective lens frame 22.
The objective lens group 21 includes, in order from the object side, a first group G1 having a positive focal length, an aperture stop 23, and a second group G2 having a positive focal length.
The imaging element 25 is fixed to the imaging frame 26 via the positioning cover glass 24 to constitute an imaging unit.
The enlarged video module of the first embodiment performs focus adjustment by changing the distance 27 between the objective unit and the imaging unit.
Further, the insertion portion of the magnifying endoscope includes a distal end hard portion 28 and an outer surface portion 30.
The enlarged video module of the first embodiment is fixed in the insertion portion via the intermediate member 29.
As shown in FIG. 1B, the intermediate member 29 is provided with a notch portion on the outer periphery, and an illumination fiber 31 is housed in that portion and fixed to the insertion portion.
In the enlarged video module of the first embodiment having such a configuration, the video module is inserted and fixed after the intermediate member 29 and the illumination fiber 31 are fixed to the distal end hard portion 28.

Further, when the imaging magnification or the like needs to be adjusted, the enlarged video module of the first embodiment performs the adjustment by increasing or decreasing the interval between the interval adjusting units 32a and 32b provided before and after the brightness stop 23. Can do. For the interval adjustment, an interval adjustment ring made of a very thin plate material is used.
For this reason, the interval adjusting portions 32a and 32b are designed on the assumption that a plurality of thin plates are stacked in advance, and the interval after assembling the components varies due to the finished dimensional tolerance of the actually used components. Accordingly, adjustment is performed by increasing or decreasing the number of thin plates.

Next, numerical data of optical members constituting the enlarged video module of the first embodiment will be shown.
Numerical data 1
Surface number Curvature radius Interval Refractive index Abbe number Lens outer diameter
1 INF 0.46 1.5183 64.14 1
2 0.84 0.17 1
3 INF 0.4 1.7323 54.68 1
4 -0.817 0.05 1
5 1.353 0.65 1.7323 54.68 1
6 -0.703 0.25 1.7044 30.131
7 -3.804 0.09 1
8 INF (Aperture) 0.03 1
9 INF 0.4 1.5156 75.00 1
10 INF 0.2 1
11 1.566 0.4 1.67 48.32 1
12 -1.566 0.2 1
13 -0.729 0.3 1.5198 52.43 1
14 INF 0.56 1
15 INF 0.4 1.5183 64.14
16 INF 0.01 1.5119 63.00
17 INF 0.4 1.6138 50.20
18 INF 0.01 1.5220 63.00
19 INF 0
Object distance 0 Image height 0.500

Second Embodiment FIGS. 2A and 2B are diagrams showing an optical configuration of a second embodiment of the enlarged video module of the present invention. FIG. 2A is a cross-sectional view, and FIG. 2B is a cross-sectional view as viewed from the direction of arrow A in FIG. is there. The basic configuration of the second embodiment is substantially the same as that of the first embodiment, and similar components are denoted by the same reference numerals, and description thereof is omitted.
Next, numerical data of optical members constituting the enlarged video module of the second embodiment will be shown.

Numerical data 2
Surface number Curvature radius Interval Refractive index Abbe number Lens outer diameter
1 INF 0.88 1.8882 40.76 1.2
2 -0.703 0.05 1
3 INF 0.4 1.5183 64.14 1.2
4 -1.485 0.05 1
5 2.085 0.76 1.8081 46.57 1.2
6 -0.703 0.25 1.8126 25.42 1.2
7 INF 0.05 1
8 INF (Aperture) 0.03 1
9 INF 0.4 1.5156 75.00 1.2
10 INF 0.43 1
11 1.131 0.5 1.8395 42.72 1.2
12 -3.127 0.2 1
13 -1.061 0.3 1.8126 25.42 1.2
14 INF 0.2 1
15 -0.592 0.3 1.8081 46.57 1.2
16 2.132 0.77 1.8126 25.42 1.2
17 -1.262 0.77 1
18 INF 0.4 1.5183 64.14
19 INF 0.01 1.5119 63.00
20 INF 0.4 1.6138 50.20
21 INF 0.01 1.5220 63.00
22 INF 0 1
Object distance 0 Image height 0.500

Next, the conditional expression parameters of the first and second embodiments are shown in Table 1, and the values of the conditional expressions are shown in Table 2, respectively.
Table 1
Item Symbol Unit First Example Second Example Objective Magnification βo -2.678847 -6.63
Front group focal length f1 [mm] 0.765 0.591
Rear group focal length f2 [mm] 3.476 4.557
Focal length f [mm] 0.657 0.797
Half viewing angle wy [deg] 6.141 3.95
Chief ray emission angle wy '[deg] 13.965 6.02
Object side numerical aperture NA 0.2184 0.55
Diaphragm diameter φ1 [mm] 0.36 0.66
Maximum lens diameter φ2 [mm] 1 1.2
Pitch P [μ] 4 4
Reference wavelength λ [μ] 0.546 0.546

Table 2
No. Conditional expression First embodiment Second embodiment
1 0.9 ≦ | coswy '/ coswy | ≦ 1.1 0.976 0.997
2 0.2 ≦ φ1 / (φ2 × f1) ≦ 2 0.471 0.931
3 0.1 ≦ | p × (NA) ² /(0.61×λ×βo)|≦0.8 0.215 0.544
4 1 <| βo | <10 2.680 6.630
5 0.1 ≦ NA ≦ 0.8 0.220 0.550
6 2 ≦ f2 / f1 ≦ 10 4.544 7.711

Next, embodiments of the focus position adjustment method, focus range confirmation method, focus position adjustment device, and focus range confirmation device of the enlarged video module of the present invention will be described.
FIG. 3 is a schematic configuration diagram showing an embodiment of the focus position adjustment and focus range confirmation device of the enlarged video module of the present invention.
The focus position adjustment and focus range confirmation device of the enlarged video module of the present embodiment includes a substrate 4, an illumination unit 6, a light source 12, an image signal processing device 7, a processing unit 10, monitors 8, 11 and a micro. Sensors 9 and 13 are provided.
The enlargement video module includes an image pickup unit 2 including an image pickup device 3 and an objective unit 1 including a lens group. The objective unit 1 and the imaging unit 2 are configured in the same manner as the objective unit and the imaging unit in the enlarged video module of the embodiment shown in FIG. 1 or FIG.

  The substrate 4 includes holding members 4a and 4b for holding the enlarged video module, a Z stage 4c capable of moving the holding member 4b in the Z direction with respect to the holding member 4a, and a holding member for the substrate 4. A Z stage 4d capable of moving 4a in the Z direction is provided. The substrate 4 holds the illumination unit 6 and can move the Y stage 4e in the Y direction, and the α gonio stage 4f and β gonio stage that can move the Y stage 4e in the α and β directions. 4g, an α gonio stage 4f, a β gonio stage 4g, an X stage 4h capable of moving in the X direction, and a Z stage 4i capable of moving the X stage 4h in the Z direction.

In the enlarged video module, the image pickup unit 2 including the image pickup device 3 is held by the holding member 4b, and the objective unit 1 including the lens group is held by the holding member 4a, and is adjusted in the Z direction to adjust the focus position. It is provided on the substrate 4 so as to be movable and fixed.
The microsensor 9 indicated by an arrow and whose detailed configuration is omitted is configured to acquire position information of the image sensor 3 in the Z direction in submicron units.
The illumination unit 6 is held by the Y stage 4e. The subject 5 used for focus adjustment is illuminated from the back by the illumination unit 6 and is provided on the substrate 4 in a state where it can be adjusted and fixed in the XYZ and αβ directions with respect to the objective unit 1.
The light source 12 supplies illumination light to the illumination unit 6.
The image signal processing device 7 is configured to perform control to display an image on the monitor 8 after converting an image of a subject projected on the image sensor 3 and converted into a signal through the image sensor 3 into an image signal. . Further, the image signal processing device 7 is configured so as to be able to control the amount of light so as to obtain optimum brightness in cooperation with the light source 12.
The processing unit 10 is configured to calculate the contrast value of the image signal and to control the monitor 11 to display the calculation result.

A contrast detection method in the focus position adjustment and focus range confirmation apparatus of the enlarged video module of the present embodiment configured as described above will be described with reference to FIG. FIG. 4 (a) is an explanatory view showing a transmission specimen in which white and black bands are alternately arranged as an example of a subject used for contrast detection, and FIG. 4 (b) is a photograph of the transmission specimen shown in FIG. 4 (a). It is a graph which shows the image signal acquired when it scans in the direction of an arrow, and shows the signal waveform which carried out the time average of the spatial luminance signal acquired during imaging time. In the figure, the vertical axis represents luminance, and the horizontal axis represents the scanning direction.
When the maximum value of the detection waveform corresponding to the monochrome position of the subject is Imax and the minimum is Imin, the contrast I can be obtained as follows.
I = (Imax − Imin) / (Imax + Imin)

FIG. 5 is a graph in which the contrast obtained by the method described with reference to FIG. 4 is plotted for each imaging surface position of the imaging device.
Let us consider a case where the imaging position where the subject is in the best focus state (imaging surface position of the imaging element where the luminance reaches a peak) is zm0, and this position zm0 is obtained.
At the imaging surface positions zm1 and zm1 ′ in the vicinity of the imaging surface position zm0 in the best in-focus state, the contrast change ΔIm1 is very small, and it is difficult to detect zm1 and zm1 ′ with high accuracy.
On the other hand, for example, if the contrast change amount ΔIm2 is set to be sufficiently large so that ΔIm3 is 20%, the imaging surface positions zm2 and zm2 ′ can be detected with high accuracy, so that the best match is obtained from the two position information zm2 and zm2 ′. The imaging surface position zm0 that is in a focused state can be obtained with high accuracy.

In addition, in an optical system in which spherical aberration is corrected satisfactorily, the contrast curves before and after the in-focus position are symmetrical.
Therefore, by calculating the midpoint of the imaging plane positions zm2 and zm2 ′, the value of the imaging plane position (luminance peak position) zm0 that achieves the best in-focus state can be obtained.
On the other hand, in the case of an optical system in which the influence of spherical aberration cannot be eliminated, the contrast peak position does not coincide with the midpoint of zm2 and zm2 ′ and is shifted before and after the midpoint. In an optical system having an imaging magnification greater than 1, the image side error (in this case, the amount of deviation between the best image plane position and the actual image pickup element position of the image sensor) is reduced and projected to the object side. The resolution within the depth of field of the objective optical system does not deteriorate significantly.
If necessary, such a deviation can be corrected as appropriate after evaluating the depth of field by a method described later.
According to the focus adjustment method described above, it is possible to adjust the focus by detecting the position of the imaging surface in the best focus state for a subject set at a certain distance.

  After the focus adjustment, it is necessary to evaluate the depth of field of the objective optical system of the video module and verify the validity of the position of the subject used for the focus adjustment with respect to the enlarged video module. Next, the method will be described.

The change in contrast with respect to the position of the subject (for example, the distance from the tip of the objective optical system of the enlarged video module) is shown in the graph of FIG. The graph of FIG. 6 is a plot of the contrast value when the position of the subject is changed in a state where the position of the imaging surface of the imaging device is fixed at the position where the best focus state is achieved in the above-described focus adjustment. It is.
In this case, the contrast becomes maximum at the installation position zo0 of the subject used for focus adjustment, and decreases as the subject moves away from the position zo0. In the figure, distance 0 means a state in which the subject and the object-side tip surface of the objective optical system of the enlarged video module are in contact with each other, and is a reference position for detecting the distance of the subject.

In this embodiment, the allowable lower limit value of the observable contrast is set to a certain value, for example, 20%, and the object optical system of the video module after focus adjustment is detected by detecting the position of the subject that is the lower limit value. To evaluate the validity of the focus position. In the graph of FIG. 6, the depth of field is in the range of 0 to zo1.
Here, as a result of evaluating the depth of field, when it is unsatisfactory in the range up to zo1 and the contrast at the position 0 in contact with the subject seems excessive, for example, as shown in FIG. The subject position is corrected to a position zo2 farther from the object-side tip surface of the objective optical system than the subject installation position zo0 used for focus adjustment, and focus adjustment is performed again to obtain a contrast curve shown in FIG. In the graph of FIG. 7, the depth of field of the objective optical system is expanded to 0 to zo3.

  Using the above method, the appropriateness of the position where the subject is placed during focus adjustment is evaluated so that the optimum depth of field can be obtained, and the position is corrected as necessary. Note that the final evaluation of the depth of field of the objective optical system involves not only adjustment errors but also subjective factors. Therefore, after the focus position is tentatively determined by the above-described focus adjustment means, it is possible to correct the final focus position in consideration of a subjective impression of image evaluation.

When the subject position is moved in the focus position adjustment and focus range confirmation device of the enlarged video module of the present invention, it is necessary to provide means for accurately detecting the subject position.
For this reason, with the focus position adjustment and focus range confirmation device of the enlarged video module of the present embodiment, the position in submicron units of contact type or non-contact type, which is indicated by arrows in FIG. A microsensor 13 for detection is provided. For this reason, the position of the subject can be detected with high accuracy.
The micro sensor detects the position in sub-micron units and can be equipped with an arithmetic circuit that calculates and removes mechanical errors associated with the fixation and movement of the subject so that the position of the moving subject itself can be accurately measured. preferable.

Note that the movement of the subject itself may be performed using a microstage or a step motor as long as the unit movement amount is as fine as submicron.
In addition, when the reference position for obtaining the position where the subject is set is the object side front end surface of the objective optical system of the enlarged video module, the contact position between the subject and the front end surface of the objective optical system can be accurately detected. I need it.

In the focus position adjustment and focus range confirmation device of the present invention, if the subject is pushed beyond the contact state with the object side tip surface of the objective optical system, the subject is pressed and deformed, or the subject optical system is not deformed. An inclination is generated.
When an image is observed through the objective optical system from the time when the subject starts moving toward the front end surface of the objective optical system, the image is in a direction perpendicular to the movement of the subject, that is, the center of the visual field when the subject is deformed or tilted. On the other hand, since movement starts in the vertical and horizontal directions, it is possible to detect a state where the subject and the front end surface of the objective optical system are in contact with each other by detecting this image change.
Furthermore, in the objective optical system used in the video module of the present invention, the slight inclination of the subject with respect to the objective optical system is enlarged and projected onto the image side, so the focus adjustment and focus position confirmation device detects the posture of the subject. In addition, a mechanism for correcting as necessary is provided.
For example, since the depth of field range of the objective optical system of the present invention is very narrow, and the distance between the subject and the object-side tip surface of the objective optical system is very close, interference fringes generated between these objects can be reduced. It is possible to detect the posture of the subject by using it. By recording an interference fringe image when the subject's posture is appropriate in advance and comparing it with the interference fringe when the subject is moved, the subject's posture is always kept in an appropriate state even when focus adjustment is repeated. Focus adjustment can be performed with good reproducibility. A collimator or the like can also be applied as other position detection means.
Further, the tilt correction can be adjusted by, for example, the gonio stages 4f and 4g provided on the subject side shown in FIG.

  According to the above method, it is possible to improve reproducibility and focus adjustment accuracy compared to a conventional focus adjustment method in which subjects are set at a plurality of distances.

In addition, since the depth of field range of the objective optical system of the present invention is very narrow and the distance between the subject and the object side tip surface of the objective optical system is very close, when determining the installation position of the subject The measurement of the distance from the reference position can be omitted, and the subject can be positioned by devising the subject, for example.
When it is necessary to place the subject at a distance of several μm from the reference position, a transparent film manufactured with submicron thickness is formed on the subject surface by means such as vapor deposition, and the subject is placed on the reference surface. The object can be accurately placed at a desired distance simply by striking against the object. Since the film thickness of the transparent film can be controlled in nanometer units, it has sufficient accuracy to set the distance between the subject and the reference plane.
In addition, when it is necessary to install a subject at a position where the distance from the reference position is about several tens of μm, a thin plate processed by adjusting the thickness in micron units between the subject and the reference surface is sandwiched between It is also possible to place a subject accurately at a distance. For example, if an etching process at the time of semiconductor manufacture is used, the thickness of the thin plate can be controlled in units of microns, so that sufficient accuracy can be secured for setting the distance between the subject and the reference surface.
Thus, the accuracy of the distance between the subject and the reference plane can be ensured with a single component, so that iterative repeatability in focus adjustment can be improved.
For example, in the case of a transmission type specimen in which white and black bands shown in FIG. 4A are alternately arranged as a subject to be used for focus adjustment, the width of the band needs to be aligned to a length of about submicron. However, it is possible to use a transparent substrate made of glass or the like by applying an etching process at the time of manufacturing a semiconductor, or a diffraction grating.

In the apparatus for adjusting the focus position and the focus range confirmation of the enlarged video module of the present embodiment configured as described above, the focus position is adjusted and the focus range is confirmed and corrected according to the procedure shown in FIG.
First, the focus position adjustment procedure will be described.
The objective unit 1 is inserted to a position where it comes into contact with the imaging unit 2 (step S1). Next, the fitting state (tilt) of both units is adjusted and fixed to the holding members (jigs) 4a and 4b on the substrate 4 (step S2). Next, the subject 5 is attached so as to be fixed to the illumination unit 6, and then moved so as to come into contact with the front end surface of the objective unit 1 via the Z stage 4i (step S3). Next, in this state, the imaging unit 2 is moved through the Z stage 4c so as to focus on the subject while observing images and contrast values displayed on the monitor 8 and the monitor 11 (step S4). Next, the position of the subject 5 with respect to the objective unit 1 at this time is detected via the microsensor 13. Alternatively, the inclination and position of the subject 5 with respect to the objective unit 1 are detected by detecting interference fringes due to the reflected light of the subject 5 and the reflected light of the front end surface of the objective unit 1 by means of interference fringe detection means (not shown) (step S5). ).

  Next, the reflected light of the subject 5 and the objective unit 1 detected via the interference fringe detection means (not shown) via the X stage 4h, the Y stage 4e, the Z stage 4i, the α gonio stage 4f, the β gonio stage 4g, etc. The position and inclination of the detected subject 5 are adjusted so that the interference fringes caused by the reflected light from the front end surface of the subject will be in a desired state (step S6). Then, the adjusted position of the subject 5 is stored as a reference position (origin) in contact with the objective unit surface in an optimum state (step S7). Next, the subject 5 is moved via the Z stage 4i to a position that is a predetermined distance away from the origin serving as a reference for focus adjustment.

  Next, the imaging unit 2 is moved in a direction away from the position where it contacts the objective unit 1 via the Z stage 4c (step S9). At this time, the contrast of the subject 5 corresponding to the position of the moving imaging unit 2 is detected and displayed on the monitor 11 via the processing unit 10 (step S10). Next, the best focus position is obtained from the two positions of the image pickup unit 2 having a desired contrast value (step S11). Next, the imaging unit 2 is moved to the best focus position via the Z stage 4c (step S12). Thereby, the focus position of the enlarged video module is adjusted to the optimum position.

Next, the focus range confirmation procedure will be described.
In the state where the focus position of the enlarged video module is adjusted as described above, the subject 5 is moved to the surface (origin) of the objective unit 1 via the Z stage 4i (step S21). Next, while detecting the position of the subject 5 via the microsensor 13, the subject 5 is moved away from the surface (origin) of the objective unit 1 via the Z stage 4i (step S22). At this time, the contrast of the subject 5 corresponding to the position of the moving subject 5 is detected and displayed on the monitor 11. When the contrast is far enough to reach a predetermined lower limit, the movement of the subject 5 is stopped (step S23). Then, the focus range is obtained from the position of the subject 5 at this time (step S24). Next, the validity of the focus range is examined (step S25). If the focus range satisfies the desired range, the position of the subject 5 is fixed and the focus range confirmation process is terminated (step S26).

When the focus range does not satisfy the desired range, the focus range is corrected by the following procedure.
The distance at which the subject 5 is placed is corrected via the Z stage 4i, and the above-described steps S8 to S26 are repeated (step S31).
As described above, by using the focus position adjustment method and the focus range confirmation method of the present embodiment, the enlarged video module can be accurately adjusted with the optimum depth of field.

In accordance with expansion video module of the present invention, to achieve the enlarged endoscope having a high imaging magnification and high resolution accuracy focus adjustment miniature optimal depth of field to cells in vivo real-time Can be observed.

It is a figure which shows the optical structure of 1st Example of the expansion video module of this invention, (a) is sectional drawing, (b) is sectional drawing seen from the arrow A direction in (a). It is a figure which shows the optical structure of 2nd Example of the expansion video module of this invention, (a) is sectional drawing, (b) is sectional drawing seen from the arrow A direction in (a). It is a schematic block diagram which shows one Example of the focus position adjustment apparatus and focus range confirmation apparatus of the expansion video module of this invention. It is a diagram for explaining the contrast detection method in the focus position adjustment device of the enlarged video module of the present embodiment, (a) is an explanatory diagram showing a black and white transmission sample as an example of a subject used for contrast detection, (b) is ( It is a graph which shows the image signal when the monochrome transmission sample shown to a) is image | photographed. It is the graph which plotted the contrast calculated | required with the said method demonstrated using FIG. 5 for every position of the image pick-up element. It is a graph which shows an example of the change of contrast to the position of a subject (distance from the object side tip surface of the objective optical system of an expansion video module). It is a graph which shows the other example of the change of the contrast with respect to a to-be-photographed object's position (distance from the object side front end surface of the objective optical system of an expansion video module). It is a flowchart which shows a series of procedures concerning one Example of the focus position adjustment method and focus range confirmation method of the expansion video module of this invention. It is explanatory drawing which shows an example of the conventional focus adjustment method of an endoscope.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Objective unit 2 Imaging unit 3 Imaging device 4 Board | substrate 4a, 4b Holding member 4c, 4d, 4i Z stage 4e Y stage 4f (alpha) gonio stage 4g (beta) gonio stage 4h X stage 5 Subject 6 Illumination unit 7 Image signal processing apparatus 8, 11 Monitors 9, 13 Microsensor 10 Processing unit 12 Light source 21 Objective lens group 22 Objective lens frame 23 Brightness stop 24 Positioning cover glass 25 Imaging element 26 Imaging frame 27 Distance 28 between objective unit and imaging unit Hard tip portion 29 Intermediate member 30 Endoscopic outer surface part 31 Illumination fibers 32a and 32b Interval adjustment part G1 First lens group G2 Second lens group

Claims (4)

Oite expansion video module the imaging magnification with a greater than one objective optical system and the imaging device,
The objective optical system includes, in order from the object side, a front group having a positive focal length, and an aperture stop,
An enlarged video module characterized by satisfying the following conditional expression:
0.9 ≦ | coswy ′ / coswy | ≦ 1.1
0.2 ≦ φ1 / φ2 / f1 ≦ 2
Where wy ′ is the incident angle of the principal ray corresponding to the maximum viewing angle in the magnified video module to the imaging surface of the imaging device, wy is the half viewing angle, φ1 is the aperture diameter of the aperture stop, and φ2 is the objective. The maximum outer diameter of the optical system, f1, is the focal length of the front group. Oite expansion video module the imaging magnification with a greater than one objective optical system and the imaging device,
An enlarged video module characterized by satisfying the following conditional expression:
0.1 ≦ | p × (NA) ² /(0.61×λ×βo)|≦0.8
Here, p is the pixel size of the imaging device, NA is the object-side numerical aperture of the objective optical system, λ is the e-line wavelength 0.546 [μm], and βo is the magnification of the objective optical system. A step of fixing the position of the object at a predetermined distance relative to the object side front end surface of the front Symbol objective optical system,
Moving the image sensor to detect two positions of the image sensor at which a subject image has a predetermined contrast;
Obtaining the position of the image sensor that maximizes the contrast of the image of the subject from the two detected positions;
The method of manufacturing an enlarged video module according to claim 1, wherein the focus position is adjusted through the steps. Bringing a subject into contact with the object-side tip surface of the objective optical system;
Moving the position of the subject in the direction of the optical axis of the objective optical system so as to obtain a predetermined contrast;
Detecting the position of the subject having a predetermined contrast;
3. The method of manufacturing an enlarged video module according to claim 1, wherein the focus range is confirmed through the following steps.

Images