Objective for stereomicroscopes of the telescope type

Details Objective for stereomicroscopes of the telescope type Objective for stereomicroscopes of the telescope type

2003-06-04

2004-04-06

Epps, Georgia (Department: 2873)

Optical: systems and elements

Lens

Microscope objective

C359S659000, C359S656000

Reexamination Certificate

active

06717739

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to a high resolution objective for stereomicroscopes of the telescope type which contains three optical assemblies, the first assembly being arranged towards the object end and the third assembly being arranged towards a magnification changer.
DESCRIPTION OF THE RELATED ART
Stereomicroscopes are usually equipped with a magnification changer which on the one hand allows high magnification of the object and on the other hand makes it possible to view large object fields. These devices are used for example in technology, for manipulating and inspecting small objects such as, for example, semiconductor structures or micromechanical objects, in research institutes involved in biosciences and materials science and also, for example, for examining and manipulating cells or for surgical purposes. In the course of miniaturising and researching into ever smaller preparations, the requirements imposed on the resolution of these microscopes are increasing and on the other hand the size of the field of vision becomes more important with less magnification for rapid positioning of the slides and for improving the overall view in observations.
In order to vary the magnification of a stereomicroscope magnification changers (the telescopic or zoom principle) are inserted behind the objective. The ratio of maximum to minimum magnification is designated z. Using a zoom the magnification can be varied smoothly over a particular range. Afocal zooms are known which image object rays from infinity to infinity and allow the magnification to be varied without altering the position of the object and the image.
FIG. 1
shows the basic structure of a stereomicroscope of the telescope type. The stereomicroscope allows the user, whose eyes are indicated as
8
R and
8
L, to obtain a three-dimensional impression of the object
1
being observed. The object
1
, which is in the front focal point of the objective
2
, is imaged using two separate optical channels. The two viewing channels
10
L and
10
R are of similar construction and each contain a magnification changer system
3
L,
3
R, a tube lens
4
L,
4
R and an eyepiece
7
L,
7
R. Image reversing systems
5
L,
5
R mounted behind the tube lenses
4
L,
4
R provide upright intermediate images
6
L,
6
R on the correct side which are visually viewed using the pair of identical eyepieces
7
L,
7
R. These pairs of optical elements are arranged parallel and symmetrical to the axis of the objective
2
. The two magnification changers
3
L,
3
R alter the magnification selectively but in the same way for the left and right hand channels
10
L,
10
R.
The two intermediate images
6
L and
6
R are different images of the object
1
as the object
1
is viewed at an angle wL in the left hand channel
10
L and at an angle wR in the right hand channel
10
R. In this way it is possible to view the object
1
stereoscopically in the same way as when looking directly at an object through the eyes
8
L,
8
R. The two different images are processed in the brain to form a three-dimensional image impression.
EP denotes the diameter of the entry pupil of the magnification changers
3
L,
3
R which are adjustable in the same way. uL and uR denote the half aperture angles of the cone with the vertex in the centre of the object OM, which is bounded by the entry pupil. uL and uR are the same size, as the microscope is symmetrical with respect to the axis
9
of the objective
2
. Consequently, uL and uR may both be referred to as u. As wR and wL are not large, the equation EP=2×F×sin(u)=2×F×nA applies here, where nA is the effective numerical aperture (in air) of the objective, based on the entry pupil of the magnification changer
3
L or
3
R downstream of the objective
2
and F is the focal length of the objective
2
, this equation being known for well corrected optical systems which satisfy the sine condition. With a wavelength of &lgr;=550 nm the resolution capacity is 3000×nA as a rule of thumb (in pairs of lines per mm). Thus, a high aperture is a prerequisite for a high resolution.
At the maximum magnification of the magnification changer
3
L,
3
R the entry pupil diameter EP is at its maximum and is then known as ENP. The magnification changers shown may be the afocal zooms or telescope systems mentioned earlier.
FIG. 1
also shows the path of a ray running from the lower edge of the object Ou to the edge of the intermediate image. It forms an angle w in the space between the objective and the magnification changer with the axis
9
of the objective
2
. w is the field angle of the objective
2
, which is at its maximum when the magnification of the magnification changer
3
L and
3
R is at its weakest. The maximum value of w is hereinafter referred to as w
1
. The object width, i.e. the spacing of the object
1
from the first surface of the objective
2
, is designated OW.
FIG. 1
shows the objective
2
purely diagrammatically. As a rule, the objectives form lens systems consisting of individual lenses and/or cemented lenses (cemented members).
Published Japanese Application JP 2001-147378 discloses an objective system for a stereomicroscope which consists of three sets of lenses, the two outer sets of lenses having a positive refractive power while the central set of lenses comprises at least one cemented member consisting of three lens elements. In one embodiment by way of example, the lens assembly at the object ends consists of a single lens followed by the second lens assembly which contains two cemented members having three or two cemented lenses, which is in turn followed by the third lens assembly consisting of a cemented member with two lenses. This structure is intended to suppress the optical imaging errors, distortion and chromatic aberration as far as possible. The embodiments published have a numerical aperture nA of 0.13 and 0.20. The resolution of these objectives is thus within the known range.
Published Japanese Application JP 101 70 832 A describes a conversion lens which can be placed in front of the objective in a stereomicroscope and in conjunction with this main objective produces a short focal length. As a result of the high magnification produced, the conversion lens is used for viewing extremely small object structures while in order to observe the object in a large field of vision the conversion lens can be removed. The disadvantage of such a construction is the high number of lenses used and the need to install or remove a conversion lens. The proposed combination consists of a total of twelve lenses. The conversion lens in the publication referred to consists of three lens assemblies of which the two outermost have positive refractive power and each consist of two cemented lenses while the central lens assembly is a cemented component in the shape of a meniscus. The actual main objective, viewed from the object end, consists of a single lens followed by a cemented member consisting of two lenses, followed by another cemented member comprising two lenses and another single lens.
Olympus provide a conversion lens of this kind under model reference SZX-AL20. The combination of conversion lens and objective has a numerical aperture of nA=0.275 but can only be used in a limited range of the zoom, outside which the image is cut by vignetting. The object spacing OW of the combination of objective and conversion lens is only about 10 mm, thus making it substantially more difficult to work with objects under the microscope.
The present applicants have marketed a stereomicroscope under model reference “MZ 12” for which objectives with a focal length of F=50 mm and a maximum entry pupil diameter of ENP=20 mm are available. In this objective, which already has a high magnification, the spacing of the object from the first surface of the objective OW=21.3 mm, making it possible to work with objects under acceptable conditions.
Finally, U.S. Pat. No. 4,640,586 discloses an objective for a stereomicroscope of the telescop

Affiliated with

Also associated with

Rating

Objective for stereomicroscopes of the telescope type does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Objective for stereomicroscopes of the telescope type, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Objective for stereomicroscopes of the telescope type will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3210727