JP2000292707A - Microscope optics - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the unevenness of the brightness of observation field caused by the insufficiency of the peripheral light quantity of an illumination system by arranging a light quantity damping filter whose transmissivity is changed in a radial direction from the center orthogonally to an optical axis. SOLUTION: The transmissivity characteristic of an ND filter 5 functioning as the light quantity damping filter is set to obtain the darkness nearly the same as an outside dark area. The brightness of an observed image 7 is averagely lowered but the light quantity distribution of the entire field is nearly uniform both at the center part and the peripheral part, so that the insufficiency of the peripheral light quantity becomes inconspicuous. In the case of a microscope, it is desirable to arrange the ND filter 5 in the vicinity of an image position because the principal light beam angle of the image is small and axial luminous flux is largely overlapped on off-axis luminous flux as going away from the image. When the ND filter 5 is installed at the image position, the dust or the scratch of the filter is seen, so that it is good to arrange the ND filter 5 to be somewhat deviated from the image position. It is good to arrange the light quantity damping filter 5 is at or near a conjugate position to the sample 2 of an illumination system 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a microscope optical system.

[0002]

2. Description of the Related Art Hitherto, in a microscope, an illumination optical system and a condenser optical system have been proposed in order to realize a uniform and wide illumination visual field in order to make the peripheral light amount shortage of the visual field inconspicuous. No. 33820, JP-A-8-1
01344). In order to correct the shortage of the light amount on the peripheral surface of the illumination system, a lens having a light absorbing film on the lens surface (see JP-A-54-66155) has been proposed.

In general, in an ultra-wide-angle camera lens, the transmittance near the center is the lowest on the front surface of the lens, and the transmittance continuously increases in the radial direction from the center in order to make the shortage of peripheral light inconspicuous. A device provided with a light amount attenuation filter is known.

[0004]

However, those using the above-mentioned conventional illumination optical system and condenser optical system have problems that the lens design is difficult and the lens configuration becomes complicated. Further, in the case where a light absorbing film is provided on the lens surface or the case where a liquid crystal plate is used, there is a problem that not only loss of light amount as a whole but also disadvantage in cost is caused.

[0005] Further, since the ultra-wide-angle lens of a camera and the lens of a copier have a very large angle of view, a filter or a light absorbing film having a low transmittance at the center portion is arranged beside the projection lens, so that the center of the image is reduced. Although the brightness of the part and the peripheral part can be corrected independently, in a microscope, the angle of view is very small and close to the pupil in the vicinity of the objective lens, so the luminous flux of the central part of the image and the peripheral part largely overlap, so Even if a similar filter or light absorbing film is placed near the objective lens, it is not possible to independently correct the brightness of the central part and the peripheral part of the image.

Originally, the causes of the peripheral light quantity shortage can be classified as follows. That is, 1) an object lens, an eyepiece, etc., based on the cos 4 power law, and vignetting (calibration) of off-axis rays, 2) cos of the illumination system
This is based on the fourth power law, vignetting of off-axis dependent rays, and 3) that a large illumination range cannot be obtained in principle due to insufficient light source area of the illumination system. Regarding the above 1), the angle of view on the image side is at most less than 10 degrees in the microscope, the dimming due to the cos 4 law is small, and the vignetting of off-axis dependent rays is avoided in design, so that there is no practical problem. The above 2) is not designed as much as 1) but is avoided. The above 3) is the largest cause.

Usually, a filament is used as a light source.
This is because the light source area is small, and the microscope shows a large NA (0.9 in a dry system) according to Lagrangian Helmholtz's law.
It is known that it is difficult to illuminate a wide field of view (diameter of 20 mm or more) of 5) or a low-magnification objective lens. To compensate for this, a light diffusing plate is usually inserted into the illumination system to artificially increase the area of the light source, but this is not sufficient.
Therefore, when using a low-magnification objective lens as a result,
Insufficient amount of light around the image. For this reason, various contrivances have been conventionally made on the illumination system (Japanese Patent Laid-Open No. 9-33820,
Japanese Patent Laid-Open No. 8-101344) is not effective in practice.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to eliminate unevenness in the brightness of an observation field due to insufficient peripheral light of an illumination system. It is intended to provide a microscope that has been developed.

[0009]

In order to achieve the above object, a microscope optical system according to the present invention is arranged such that a microscope optical system is located near an image forming position of an objective lens or near a position conjugate with the image forming position of the objective lens. It is characterized in that a light quantity attenuation filter whose transmittance changes in the radial direction is arranged so as to be orthogonal to the optical axis.

According to the present invention, the transmittance of the light amount attenuating filter is selected so that it is lowest near the center and continuously increases in the radial direction from the center.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below with reference to the illustrated embodiments. FIG. 1 is a schematic configuration diagram of one embodiment of a microscope optical system according to the present invention. In the drawing, 1 is an illumination system, 2 is a sample, 3 is an objective lens, 4 is an intermediate image, 5 is a light amount attenuation filter, and 6 is an eyepiece. The lens or photographic lens 7 is an observation image. In this case, the intermediate image 4 is insufficient in peripheral light quantity (the amount of decrease in peripheral light quantity is determined by the cos 4 power law of the objective lens itself and the decrease in peripheral light quantity due to vignetting of off-axis dependent rays and the insufficient peripheral light quantity of the illumination system 1). Then, as shown in FIG. 2, the amount of light decreases toward the outer periphery in the radial direction and becomes darker.
If the ND filter is made such that the transmittance characteristic of the ND filter becomes as dark (brightness) as the brightness of the outer dark area as shown in FIG. 3 (the transmittance curve is a quadratic function, The brightness of the observation image 7 is reduced on average, but the light quantity distribution of the entire field of view, as shown in FIG. It becomes substantially uniform, and the lack of peripheral light quantity becomes inconspicuous. ND filter 5
In the case of a microscope, when the chief ray angle of the image is small and away from the image, the overlap of the on-axis light beam and the off-axis light beam increases,
Preferably, it is located near the image position. However, this N
When the D filter is installed at the image position, dust and scratches on the filter can be seen. Therefore, it is actually better to dispose the D filter slightly from the image position. Note that this light amount attenuation filter 5 is used for the illumination system 1.
May be arranged at a position conjugate with the specimen 2 or near it.

Strictly speaking, it is preferable that the transmittance of the ND filter 5 increases concentrically toward the periphery in the radial direction as described above. However, when the filter 5 is arranged slightly shifted from the image position in the optical axis direction. Since the boundary is blurred, the transmittance may change stepwise as shown in FIG. That is, even in this case, the intensity (brightness) distribution of the synthesized image becomes relatively smooth as shown in FIG. Generally, in an ND filter, a filter whose transmittance changes stepwise toward the outer periphery in the radial direction is cheaper and more stable because it can be manufactured stably.
In practice, it is more advantageous to use an ND filter whose transmittance changes stepwise toward the outer periphery in the radial direction.

FIG. 7 is a schematic structural view of another embodiment of the microscope optical system according to the present invention. In the figure, optical members that are substantially the same as those used in the above embodiments are given the same reference numerals.
In this embodiment, the light absorption film having the transmittance distribution as described above is formed on at least one of the lens surface of the illumination system 1, the surface of the objective lens 3, and the surface of the eyepiece 6 (or the lens of the projection system). This is different from the above-described embodiment. This embodiment is advantageous in that the number of parts can be reduced.

As described above, the microscope optical system of the present invention has the following features in addition to the features described in the claims. (1) The microscope optical system according to claim 1, wherein the transmittance of the light amount attenuation filter is selected so as to be lowest near the center and to increase stepwise in the radial direction from the center.

(2) A microscope optical system characterized in that a light quantity attenuating film whose transmittance changes radially from the center is attached to at least one surface of the objective lens in the microscope optical system.

(3) A microscope optical system characterized in that a light quantity attenuating film whose transmittance changes in the radial direction from the center is attached to at least one surface of the eyepiece lens in the microscope optical system.

(4) The microscope optical system is characterized in that a light quantity attenuating filter whose transmittance changes radially from the center at or near a position conjugate with the specimen of the illumination system is orthogonal to the optical axis. Microscope optics.

[0018]

As described above, according to the present invention, it is possible to provide a microscope optical system having a simple structure and uniform brightness over the entire field of view.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of a microscope optical system according to the present invention.

FIG. 2 is a characteristic diagram showing a change in light amount from a central portion to a peripheral portion of a microscope image.

FIG. 3 is a characteristic diagram showing a change in transmittance from a central portion to a peripheral portion of an example of the light amount attenuation filter according to the present invention.

4 is a diagram showing a change in brightness from the center to the periphery in an observation field of view obtained when the light amount attenuation filter having the transmittance characteristic shown in FIG. 3 is incorporated in the microscope optical system of FIG. is there.

FIG. 5 is a characteristic diagram showing a change in transmittance from a central portion to a peripheral portion of another example of the light amount attenuation filter according to the present invention.

6 is a diagram showing a change in brightness from the center to the periphery in an observation field of view obtained when the light amount attenuation filter having the transmittance characteristic shown in FIG. 5 is incorporated in the microscope optical system of FIG. is there.

FIG. 7 is a schematic configuration diagram of another embodiment of the microscope optical system according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Illumination system 2 Specimen 3 Objective lens 4 Intermediate image 5 Light attenuation filter 6 Eyepiece (or photograph) lens 7 Observation image

Claims (2)

[Claims] In a microscope optical system, a light amount attenuating filter whose transmittance changes in a radial direction from a center near an image forming position of an objective lens or near a position conjugate with the image forming position of the objective lens is provided on an optical axis. A microscope optical system characterized by being arranged orthogonally. 2. The microscope optical system according to claim 1, wherein the transmittance of the light amount attenuating filter is selected so that the transmittance is lowest near the center and continuously increases in the radial direction from the center.