Optical system for variable inclination angle microscope tubes

An optical system for variable inclination angle microscope tubes, in order to shorten properly the distance between the position of the eye point and focusing handle thereby to improve the operability, comprising a first optical element for bending at right angles the light path of the incident light, a second optical element for bending twice at right angles the light path of the incident light from the first optical element, a third optical element for bending twice at right angles the light path of the incident light from the second optical element and a fourth optical element arranged to bend at right angles the light path of the incident light from the third optical element and then direct it in the same direction as of the incident light upon the first optical element, the third optical element being mounted rotatably around the optical axis of the incident light upon it and the fourth optical element being so mounted as to be able to rotate by an angle twice as large as the angle of rotation of the third optical element interlocking with the rotation of the third optical element around the optical axis of the incident light upon it. Instead of the third and fourth optical elements may be arranged a prism for bending at the right angles the light path of the incident light from the second optical element and then directing it in the same direction as of the incident light upon said first optical element. In this case, the second optical element prism are rotated integrally around the optical axis of the incident light from the first optical element and the prism is further rotated by an angle twice as large as the angle of rotation of the second optical element around the optical axis of the incident light upon it.

BACKGROUND OF THE INVENTION 
a. Field of the Invention 
This invention relates to an optical system for microscope tubes. 
b. Description of the Prior Art 
A microscope so formed that the inclination angle of an observing tube may 
be variable is already known, for example, from U.S. Pat. No. 4,299,439 
and others. In such known system, as optical elements are arranged in a 
plane cutting the microscope by extending forward and rearward so as to 
vary the inclination angle of the tube, the separating distance between 
the position of the eye point of the eyepiece and the optical axis of the 
objective will be so large that there has been a problem in the operation 
that, in the case of operating the focusing handle, the hand must be 
extended greatly. 
SUMMARY OF THE INVENTION 
In view of the above mentioned circumstances, a primary object of the 
present invention is to provide an optical system for variable inclination 
angle microscope tubes wherein, in order to improve the operability, the 
distance between the position of the eye point and focusing handle can be 
made properly short. 
According to the present invention, the above mentioned object is attained 
by a variable inclination angle tube optical system including a first 
optical element for bending at right angles the light path of the incident 
light, a second optical element for bending twice at right angles the 
light path of the incident light from the first optical element, a third 
optical element for bending twice at right angles the light path of the 
incident light from the second optical element and a fourth optical 
element arranged so as to bend the light path of the incident light from 
the third optical element and to direct it in the same direction as of the 
incident light upon the first optical element, the third optical element 
being mounted rotatably around its incident light axis and the fourth 
optical element interlocked with the third optical element being mounted 
rotatably by twice the rotation angle of the third optical element around 
its incident light axis. 
According to a preferred formation of the present invention, relay lenses 
for relaying an image is arranged between the optical elements. 
According to the present invention, there can be provided this kind of 
microscope which can be so formed that, even if the inclination angle of 
the tube is varied, not only the posture of the image within the visual 
field will not vary and will be kept always stationary but also the 
separating distance between the position of the eye point and the focusing 
handle will be of a proper value, is therefore so high in the operability 
as to remarkably reduce the fatigue of the operator and is particularly 
adapted to observation for a long time. Also there can be provided a 
microscope wherein the position of the eye point can be adjusted so 
precisely and easily that the freedom of fitting the attachment is high. 
This and other objects of the present invention will become more apparent 
during the course of the following detailed description and appended 
claims.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The present invention shall be concretely explained in the following on the 
basis of the illustrated embodiments. In FIG. 1, the reference numeral 1 
represents an objective, 2 represents a prism as a first optical element 
for bending at right angles the light path of the incident light having 
passed the objective 1, 3 represents a prism as a second optical element 
arranged on the side of the prism 2 and capable of bending twice at right 
angles the light path of the incident light from the prism 2 and emitting 
the light parallelly with the incident light in the direction reverse to 
it in a position in which the optical axis is displaced, 4 represents a 
prism as a third optical element arranged to partly face the prism 3 and 
mounted so as to be capable of bending twice at right angles the light 
path of the incident light from the prism 3, emitting the light parallelly 
with the incident light in the direction reverse to it in a position in 
which the optical axis is displaced and being rotated around the incident 
light axis A.sub.1, 5 represents a prism as a fourth optical element 
arranged to be opposed to the prism 2 and to bend at right angles the 
light path of the incident light from the prism 4 and direct it in the 
same direction as of the incident light upon the prism 2 and mounted so as 
to be rotatable around the incident light axis A.sub.2, 6 represents a 
light pencil dividing prism for dividing the incident light from the prism 
5 in a left eye view light pencil and right eye view light pencil, 7 
represents a prism for bending at right angles the left eye view light 
pencil, 8 represents an eyepiece, 9 represents a prism for bending at 
right angles the right eye view light pencil and 10 represents an 
eyepiece. In this case, the prisms 2, 3, 4 and 5 are arranged in a plane 
extending in the horizontal direction of the front surface of the 
microscope body and the arrangement of the prisms 2 and 3 and arrangement 
of the prisms 4 and 5 are symmetrical with each other with the incident 
light axis A.sub.1 as an axis of symmetry. The light pencil dividing prism 
6 and the prisms 7 and 9 form well known binocular tubes and are so formed 
that, when the inclination angle of these binocular tubes is varied, while 
the prisms 4 and 5 rotate integrally around the incident light axis 
A.sub.1, the prism 5 will be further rotated by an angle twice as large 
around the incident light axis A.sub.2. 
As this embodiment is formed as mentioned above, the light having passed 
the objective 1 will proceed as indicated by the arrows through the 
eyepieces 8 and 9 and the object image will be observed. In this case, the 
image will be observed through an even number of reflections and therefore 
the initial posture of the image will be reserved as it is. In case the 
inclination angle of the binocular tubes is varied interlocking with them, 
the prisms 4 and 5 will rotate by the same angle as of the tubes around 
the incident light axis A.sub.1, at the same time, the prism 5 will rotate 
in the same direction by an angle twice as large as the angle of rotation 
of the prism 4 around the incident light axis A.sub.2 and therefore the 
image within the visual field will remain stationary. 
FIG. 2 shows an embodiment wherein relay lenses are arranged between the 
respective prisms to transmit the image. In the drawing, reference symbol 
L.sub.1 represents a convex lens arranged between the prisms 2 and 3 and 
for forming the intermediate image of the objective 1 in a position O 
within the prism 3, L.sub.2 and L.sub.3 represent respectively a concave 
lens and convex lens arranged between the prisms 3 and 4 and L.sub.4 
represents a cemented convex lens arranged betwen the prisms 4 and 5 so 
that the intermediate image formed in the position O will be relayed by 
these lenses to the front side focus positions of the eyepieces 8 and 10. 
In this case, too, the same as in the case of the already described 
embodiment, even if the inclination angle of the tubes is varied, the 
image within the visual field will remain stationary and its posture will 
not vary but the image within the visual field will be an upright image 
and will be more convenient. By the way, in this case, the magnification 
of the relay lenses will be 1.times.. As in this embodiment, making it 
possible to observe the image within the visual field as an erecting image 
by forming the image once intermediately in the optical system will be 
indispensable particularly in case the microscope is used to recognize 
patterns in the semiconductor industrial field but, in case the image 
within the visual field may be an inverted image, the relay lenses may be 
arranged to relay the object image without forming it intermediately. 
The case of applying an example of such rotating and interlocking mechanism 
of the prisms 4 and 5 as is described above to the embodiment of FIG. 2 
shall be explained in the following with reference to FIGS. 3 to 5. In the 
drawings, the reference numeral 11 represents a microscope tube supporting 
frame supporting the prism 2, lens L.sub.1 and prism 3 and removably 
fitting them to a microscope body not illustrated through a fitting part 
11a, 12 represents a photographing adaptor fitted to the microscope tube 
supporting frame 11, 13 represents a switching member fitted slidably in 
the directions indicated by the arrows as shown in FIGS. 3 and 5 and 
having a half prism or half mirror 13a and prism 13b for leading the light 
having passed the objective 1 to the prism 2 and photographing optical 
system and a cover glass fitted through hole 13c and switching operation 
grip 13d for leading the same light only to the prism 2 by switching, 14 
represents a rotary cylinder supported rotatably by the tube supporting 
frame 11 and fitted with the lenses L.sub.2 and L.sub.3 within, 15 
represents a tube frame supporting the prism 4 and mounted on the tube 
supporting frame 11 so as to be rotatable integrally with the rotary 
cylinder 14, 16 represents a rotary lens frame mounted rotatably on the 
tube frame 15, having a gear part 16a on the outer peripheral surface and 
the lens L.sub.4 within and having the prism 5 secured at the end, 17 
represents an intermediate gear borne rotatably on the tube frame 15 and 
meshed with a gear part 11b formed on the outer peripheral surface of the 
supporting frame 11 concentric with the rotary cylinder 14, 18 represents 
an intermediate gear borne rotatably on the tube frame 15, meshed with the 
intermediate gear 17 and gear part 16a of the rotary lens frame 16 and 
having the same number of teeth as of the intermediate gear 17, 19 
represents a spring stretched between the tube supporting frame 11 and 
tube frame 15 and 20 (FIG. 3) represents a spring fitted screw screwd to 
the supporting frame 11 and pressing the tube frame 15 against on the side 
wall so as not to move accidentally. According to this rotating and 
interlocking mechanism, during the observation through the eyepieces 8 and 
10, if the microscope tube is rotated, for example, counterclockwise from 
the position in FIG. 4, the tube frame 15 will rotate counterclockwise 
around its center axis together with the rotary cylinder 14 but, in such 
case, the intermediate gear 17 will rotate while revolving 
counterclockwise around the same center axis. Therefore, the intermediate 
gear 18 will rotate clockwise while revolving counterclockwise around the 
same center axis. As a result, the rotary tube frame 16 will also rotate 
counterclockwise while revolving counterclockwise around the same center 
axis. Thus, while the lenses L.sub.2 and L.sub.3, prism 4, lens L.sub.4 
and prism 5 are rotating counterclockwise integrally with the tube frame 
15 around the center axis of the rotary cylinder 14, the lens L.sub.4 and 
prism 5 will be further rotated counterclockwise by an angle twice as 
large around the center axis of the rotary tube frame 16. In this case, 
the tube frame 15 will be supported in the lower part by the supporting 
part 11c (FIG. 4) of the supporting frame 11, the tube frame 15 will be 
held as suspended by the spring 19 and therefore the tube will be stably 
maintained in the position together with the pressing action of the screw 
20 against the tube frame 15. 
Each of the above mentioned embodiments has been explained as provided with 
the binocular tubes but it is needless to say that the present optical 
system can be applied also to a microscope provided with a single 
observation tube. Also, the prism 2 may form an optical system as rotated 
by 90 degrees from the illustrated position so that the incident light 
from the objective 1 may be vertically incident upon the paper surface 
from the back side. In such case, it will be necessary to arrange the 
prism 5 also as rotated by 90 degrees. Further, mirrors can be used 
instead of the prisms as the first to fourth optical elements. The 
arrangement of the lenses is not limited to the embodiment but can be 
varied. 
Further, in the present optical system as shown by the chain lines in FIG. 
1, instead of the prism 4 which is the third optical element and the prism 
5 which is the fourth optical element, a prism 21 for bending at right 
angles the light path of the incident light from the second optical 
element 3 and directing it in the same direction as of the incident light 
upon the first optical element may be provided to attain the same object. 
In this case, it will be necessary to further rotate the prism 21 by an 
angle twice as large around the optical axis A.sub.1 while integrally 
rotating the prisms 3 and 21 around the emitted light axis from the prism 
2 toward the prism 3. FIG. 6 shows the rotating and interlocking mechanism 
for the prism 3 and 21 constituted so as to fit this embodiment. That is, 
on the microscope tube supporting frame 11 is mounted rotatably a rotary 
cylinder 22 which is rotated concentrically and integrally with the tube 
frame 15 and supports the prism 3 on its end face, on the rotary cylinder 
22 is mounted rotatably a rotary lens frame 23 having a gear part 23a on 
the outer peripheral surface, a relay lens within and the prism 21 secured 
at the end, and the gear part 23a is connected to a gear part 22a formed 
on the outer peripheral surface of the rotary cylinder 22 through a pair 
of intermediate gears arranged in the same manner as the intermediate 
gears 17 and 18 shown in FIG. 4. Accordingly, when the tube frame 15 is 
rotated around its center axis together with the rotary cylinder 22, the 
prism 3 will rotate integrally with the rotary cylinder, and the rotary 
lens frame 23 will be rotated by an angle twice as large around its center 
axis while revolving around the rotary axis of the rotary tube frame 15. 
As the formation and operation of the other parts of the mechanism shown 
in FIG. 6 are same as those of the already described embodiment, the 
further detailed explanation is omitted. According to this embodiment, 
there is a further advantage that the entire device can be more 
simplified. 
It is needless to say that such modification also falls under the scope of 
the present invention.