Patent Grant
8194328
1. Field of the Invention
The invention relates to imaging optics with adjustable optical power. The imaging optics is an optics of very general nature for use, for example, in a camera, telescope, a microscope or other optics. Furthermore, the invention relates to a method of adjusting an optical power in particular of a zoomable imaging optics.
Furthermore, the invention relates to a stereo-microscopy system for generating a magnified stereoscopic image of an object, as well as to a corresponding stereo-microscopy method.
A zoomable imaging optics is an imaging optics, the imaging ratio or magnification of which is variable.
2. Brief Description of Related Art
A conventional zoomable imaging optics comprises three lens assemblies, one of which is fixedly mounted in a support and the two other ones are displaceable along an optical axis of the optics to vary a magnification. In order to correctly displace these two lens assemblies relative to one another and relative to the fixedly positioned lens assembly, quite complex mechanics are required. Moreover, the necessary displacement of the lens assemblies requires the optics to have a relatively large minimum overall length.
From U.S. Pat. No. 4,820,028 a zoomable optics is known comprising a lens of variable optical power for changing the magnification, so that a mechanical displacement of lenses along the optical axis is not necessary. The lens of variable optical power forms part of an optics which, moreover, comprises plural lenses of fixed optical power and enables a relatively good compensation of imaging aberrations at a specific setting of the lens of variable optical power. However, if the optical power of the lens of variable optical power is varied to change the magnification, imaging aberrations occur which have a disturbing effect.
A conventional stereo-microscopy system comprises a left-hand stereo optics for generating a left-hand partial image of the stereoscopic image, as well as a right-hand partial stereo optics for generating a right-hand partial image of the stereoscopic image.
U.S. Pat. No. 6,081,372, for example, discloses a stereo-microscopy system of the so-called “Grenough” type, wherein each one of the left-hand partial stereo optics and the right-hand partial stereo optics comprises a separate objective assembly. Principal axes of both partial stereo optics are oriented at an angle relative to one another such that they intersect in an object plane of the two objective assemblies. If, in such a stereo-microscopy system, a working distance between the object plane and the objective assemblies is to be changed, the angle between the two principal axes must be changed accordingly, which renders the required mechanics unreasonably complex under practical aspects.
DE 90 16 892 U1 and U.S. Pat. No. 5,701,196 disclose stereo-microscopy systems, wherein an objective is provided for transforming an object-side beam bundle, emanating from an object plane of the objective, into an image-side beam bundle, and wherein left-hand partial stereo optics and right-hand partial stereo optics are provided in the respective image-side beam bundle and extract therefrom a left-hand partial beam bundle and a right-hand partial beam bundle, respectively, to generate therefrom the left-hand partial image and the right-hand partial image, respectively, of the stereoscopic image. The principal axes of the two partial beam bundles of the left-hand and right-hand partial stereo optics are fixedly positioned spaced apart from another and traverse the common objective also spaced apart from each other. The objective provides an optical power of a round lens. The objective comprises at least one assembly of positive optical power and one assembly of negative optical power, a distance between the two assemblies being variable to change a working distance between the objective and an object plane of the objective. In contrast to the stereo-microscopy system known from U.S. Pat. No. 6,081,372, no angle need to be changed between the principal axes of the two partial stereo optics in order to change a working distance.
The stereo-microscopy systems known from DE 90 16 892 U1 and U.S. Pat. No. 5,701,196 have proved successful in practice as far as the change of the working distance is concerned, but exhibit different optical characteristics, as against a comparable stereo-microscope with fixed working distance, i.e., wherein the working distance is not changeable. For example, in the stereo-microscopy system known from DE 90 16 892 U1, the assembly having a negative optical power is disposed closer to the object plane than the assembly having a positive optical power. Consequently, a principal plane of the objective is disposed, viewed from the object plane of the objective, behind the objective. Accordingly, a focal length of the objective is longer than a working distance between objective and objective plane. Due to the, as compared to the working distance, long focal length, the objective exhibits a total magnification, stereo impression and resolution which are diminished as compared to the corresponding objective with fixed focal length in which the focal length corresponds about to the working distance.
In the stereo-microscopy system known from U.S. Pat. No. 5,701,196, the assembly of positive optical power is disposed closer to the object plane than the lens assembly of negative optical power. As a result, a principal axis of the objective is disposed between the objective and the object plane. Accordingly, a focal length of the objective is shorter than a working distance between the object plane and the objective as such. This causes a decrease in the object field diameter and the depth of field as well as in an increase in the overall length, the overall volume and weight as compared to a corresponding objective with fixed focal length.
The present invention has been accomplished taking the above problems into consideration.
It is an object of the present invention to provide a zoomable imaging optics, wherein the required optical imaging quality is appropriately achieved by use of a lens of variable optical power.
Furthermore, it is an object of the invention to provide a method of controlling an imaging optics with variable magnification.
Furthermore, it is an object of the invention to provide imaging optics which can be easily equipped with a zoom function.
A further object of the present invention is to provide a stereo-microscopy system with variable optical properties, such as a variable working distance, which stereo-microscopy system is comparable, as far as its optical qualities and/or its overall volume and weight are concerned, with a corresponding microscopy system with fixed working distance.
According to one aspect of the invention, a zoomable imaging optics is provided which comprises at least two lenses of variable optical power disposed spaced apart from one another along a common optical axis. In order to change the imaging ratio and magnification, respectively, provided by the imaging optics, the two lenses of variable optical power are controlled oppositely, i.e., in counter direction, that is, a first one of the two lenses is controlled to increase the optical power provided by said lens, while a second one of the two lenses of variable optical power is controlled to decrease the optical power provided by the same, and vice versa.
The zoomable imaging optics may constitute a part of a larger optical system which, moreover, comprises, for example, an ocular or/and image detector or/and an objective and other optical components.
According to an exemplary embodiment, the zoomable imaging optics comprises merely the two lenses of variable optical power and no further lenses of fixed optical power.
According to a further exemplary embodiment, the zoomable imaging optics comprises at least one further lens of fixed optical power. According to this exemplary embodiment, the lens of fixed optical power is not disposed between the two lenses of variable optical power. According to an alternative exemplary embodiment, the at least one lens of fixed optical power is disposed between the two lenses of variable optical power.
An optical axis is assignable to each one of the lenses of variable optical power, so that the action of the lens of variable optical power is that of a round lens so that, moreover, a focal length is assignable to this round lens action, said focal length being variable by varying the optical power of the lens. However, this does not exclude that the lens also provides a variable optical power which is not rotationally symmetric in respect of the optical axis. Moreover, this does not exclude either that the lens of variable optical power is controllable such that the optical axis, to which the round lens action is assignable, is variable in respect of its spatial position, for example, as far as its orientation or a lateral displacement are concerned.
Due to the two lenses of variable optical power being oppositely controlled, a desired zoom effect is achievable, that is, a change in the imaging ratio. Moreover, the opposite control causes at least a partial compensation of image aberrations. An example for this is a chromatic aberration.
According to an exemplary embodiment, the zoomable imaging optics comprises at least a partial imaging optics with at least one lens of fixed optical power which may be selectively disposed in and removed from one of the beam paths traversing the two lenses of variable optical power. This allows to enlarge a range in which the imaging ratio of the imaging optics is variable. By correspondingly controlling the lenses of variable optical power, it is possible to change substantially continuously the imaging ratio over a specific range. By positioning the partial imaging optics in the beam path and by removing the same from the beam path, respectively, it is then possible, in addition, to stepwise increase and decrease the imaging ratio, respectively. According to an exemplary embodiment, the removal and insertion, respectively, of the partial imaging optics enables the imaging ratio to be changed by at least 30%.
According to a further exemplary embodiment, the partial imaging optics itself exhibits a telescopic construction, for example, that of a Galilean telescope or Keplerian telescope.
According to an exemplary embodiment, in order to fold the beam path, at least one mirror is disposed in the beam path between the two lenses of variable optical power. This enables to realize zoomable imaging optics which exhibit a particularly short overall length. As the zoomable imaging optics includes no optical components which are displaceable along the optical axis, an optical path length between successive foldings of the beam path may be particularly short and, by plural folding of the beam path, a particularly compact zoomable imaging optics is achievable.
According to a further aspect of the invention, a family of imaging optics is provided, comprising at least two imaging optics, one of which does not comprise lenses of variable optical power, the other one comprising at least two lenses of variable optical power disposed spaced apart from one another in the beam path. These second imaging optics is thus zoomable by controlling the lenses of variable optical power. The two imaging optics have specific features in common, such as, for example, geometric properties. This includes, for example, the radii of curvature and diameter of the lens surfaces and vertex distances of the lens surfaces. This allows to cost-efficiently provide a product family of optical devices which include common optical components so that the manufacture of these optical components and the assembly of the devices is rendered cost-efficiently as well. One member of the family then exhibits the zoom function due to the lenses of variable optical power, while another member of the family does not exhibit this property, but is available at lower cost.
This aspect of the invention is based on the finding of the inventors that even existing designs of imaging optics may offer a direct basis for a design of an imaging optics which is rendered zoomable by two lenses of variable optical power. In this respect, an existing design of an imaging optics can be taken as a basis which is supplemented in that two lenses of variable optical power are inserted spaced apart from each other into this existing design. If these two lenses of variable optical power are then oppositely controlled, a change in the imaging ratio provided by the optics is achieved.
According to a further aspect of the invention, a microscope with variable magnification is provided, comprising an objective for transforming an object-side beam bundle, emanating from an object plane of the objective, into an image-side beam bundle, and an image-forming assembly. The image-forming assembly may be, for example, an ocular through which the operator of the microscope views in order to directly observe optically an object disposed in the object plane. The image-forming assembly may also comprise an image detector, such as a camera, for taking an electronic image of the object.
Two lenses of variable optical power are disposed in an imaging beam path of the microscope between the object plane and the image-forming assembly, said lenses being oppositely controllable for varying the imaging ratio of the microscope, as explained above.
According to an exemplary embodiment, the two lenses of variable optical power are disposed in the objective.
According to a further exemplary embodiment, the two lenses of variable optical power are disposed in the beam path between the objective and the image-forming assembly.
According to a further exemplary embodiment, an optical assembly is provided which is selectively insertable in and removable from the beam path in order to change the imaging ratio stepwise.
According to an exemplary embodiment, the partial optics is pivotable about an axis which is oriented transversely to a direction of the beam path in order to move the partial optics into or out of the beam path.
According to a first aspect of the invention, a stereo-microscopy system is provided, comprising a left-hand partial stereo optics and a right-hand partial stereo optics for generating a left-hand partial image and a right-hand partial image, respectively, of the stereoscopic image. The stereo-microscopy system, moreover, comprises an objective commonly traversed by the left-hand and right-hand partial beam bundles of the left-hand partial stereo optics and the right-hand partial stereo optics, respectively.
The objective comprises a lens assembly of a first lens of positive optical power and a second lens of negative optical power, the indices of refraction of the lens materials of the two lenses being different from each other in order to achieve a correction of specific aberrations, such as, chromatic longitudinal aberrations and spherical aberrations. To this end, the lens assembly can be in the form of a cemented element.
The lens assembly, furthermore, comprises a third lens of variable optical power. The first, second and third lenses are disposed spaced apart from one another along the optical axis at fixed distances from one another. A focal length of the first lens and the second lens together, that is, without the third lens or, in the case that the third lens as such does not provide any optical power, is in a range between 150 mm and 450 mm. The optical power of the third lens is variable such that a working distance between the object plane of the objective and one of the first, second or third lenses of the objective is variable at least in a range of from 200 mm to 400 mm.
This allows to vary the working distance of the stereo-microscopy system, without having to displace lenses of the objective relative to one another along the optical axis of the objective.
Lenses with adjustable and variable optical power are known per se from the prior art, for example, from U.S. Pat. No. 4,795,248 or U.S. Pat. No. 5,815,233. Such lenses of adjustable optical power comprise a liquid crystal layer which is controllable via an electrode structure in order to selectively adjust an optical path length through the liquid crystal layer for a beam traversing said layer spatially dependently, that is, via a cross-section of the lens. As a result, a flexible lens action is provided. However, so far, it has not been achieved to successfully integrate such flexible lenses of adjustable optical power into a stereo-microscopy system. According to the configuration provided by the invention, however, a stereo-microscopy system with an objective is provided having a working distance which is substantially equal to the focal length of the objective.
Accordingly, the disadvantages described above in respect of the objectives, wherein the working distance differs considerably from the focal length, are reduced and advantageous properties regarding, for example, total magnification, stereo impression, resolution, overall length and weight, are achieved.
According to a further aspect of the invention, a stereo-microscopy system is provided which, again, comprises a left-hand partial stereo optics and a right-hand partial stereo optics and a common objective. Each one of the two partial stereo optics comprises a zoom optics. The two zoom optics are preferably of identical structure. However, the structure of the zoom optics of the left-hand partial stereo optics may differ from the structure of the zoom optics of the right-hand partial stereo optics. However, the structure of the two zoom optics are similar in functional respect in that each one comprises two lens assemblies disposed spaced apart from one another. Each one of the two lens assemblies comprises a first lens of positive optical power and a second lens of negative optical power, as well as a third lens of adjustable optical power. The first, second and third lenses of each lens assembly are fixedly disposed relative to one another along a principal axis of the zoom optics, and the two lens assemblies are disposed spaced apart from each other by a fixed distance along the principal axis as well. This configuration enables to provide a variable magnification of the stereo-microscopy system, without having to displace lens assemblies of the zoom optics along the principal axis of the zoom optics, as it was so far usual in prior art.
According to one embodiment, the third lens of the one lens assembly is controlled to increase the optical power of said lens, and the third lens of the other lens assembly is controlled to decrease the optical power of said lens in order to change the magnification provided by the zoom optics.
According to a further embodiment, a stereo-microscopy system is provided comprising a left-hand partial stereo optics and a right-hand partial stereo optics. Each one of the left-hand and right-hand partial stereo optics comprises an ocular with a first lens of positive optical power, a second lens of negative optical power and a third lens of variable optical power, the distances between said lenses along an optical axis of the ocular being fixed. The optical power of the third lens is adjustable in order to compensate defects of the eye of the operator of the stereo-microscopy system who views through the ocular. This allows to compensate vision defects of the eye viewing through the ocular, without components of the ocular or the ocular as a whole having to be displaced. In particular, the third lens of adjustable optical power may provide a cylinder action, so that a simple way is achieved as well of compensating an astigmatism of the eye viewing through the ocular.
According to one embodiment, a controller for controlling the third lens comprises a memory for storing values representative of the vision defects of the eyes of different users. The oculars of the stereo-microscopy system are then selectively controlled to compensate for the vision defects of one or more users. Preferably, the controller comprises a user interface which allows the respective user to select the ocular setting allocated to the respective user and to change settings in order to compensate his vision defects. The user interface may be in the form of a keyboard, a selection switch, a language control or the like.
According to a further embodiment, a stereo-microscopy system is provided, comprising a left-hand partial stereo optics and a right-hand stereo optics, each one of the two partial stereo optics comprising a separate objective. A working distance between the objectives and the object planes thereof is variable, and at least one of the two objectives comprises a wedge prism exhibiting an adjustable wedge prism action so that, even if the working distances are changed, precise stereoscopic partial images can be obtained via the left-hand and right-hand partial stereo optics, without principal axes of the partial stereo optics having to be mechanically changed as far as their orientation relative to one another is concerned.
According to a further embodiment, a stereo-microscopy system is provided, comprising a left-hand partial stereo optics and a right-hand partial stereo optics and a common objective. The common objective includes a lens of positive optical power and an optical assembly whose optical path length provided for the beams traversing said assembly is variable spatially dependently such that on each of the principal axes of the left-hand and right-hand partial stereo optics a round lens action is provided. This assembly of the objective thus provides for both partial stereo optics separate optical effects, so that said assembly of the objective may provide functions which are conventionally provided by the two partial stereo optics themselves.
In this respect, it is in particular possible to displace in simple manner the round lens action provided for the two partial stereo optics in circumferential direction about a principal axis of the objective. Accordingly, as compared to conventional solutions, the number of components of the partial stereo optics which must be displaced when the partial stereo optics are rotated in circumferential direction about the principal axis of the objective is reduced.
In particular, it is then also possible to provide simplified zoom systems in the partial stereo optics in that, when a magnification provided by the zoom systems is changed, the intensity of the round lens action can be changed as well.
The foregoing as well as other advantageous features of the invention will be more apparent from the following detailed description of exemplary embodiments of the invention with reference to the accompanying drawings. It is noted that not all possible embodiments of the present invention necessarily exhibit each and every, or any, of the advantages identified herein.
a to
a to
a to
a to
In the exemplary embodiments described below, components that are alike in function and structure are designated as far as possible by alike reference numerals. Therefore, to understand the features of the individual components of a specific embodiment, the descriptions of other embodiments and of the summary of the invention should be referred to.
Embodiments of the imaging optics according to the invention will now be described in further detail which include lenses of variable optical power. First of all, an embodiment of such a lens of variable optical power will be described below with reference to
By appropriately controlling the electrode structure 9, it is thus possible to provide for both polarization directions of the beam 17 optical path lengths of the two liquid crystal layers 3, 5, said path lengths being adjustable as a function of a position on the layers 3, 5. Accordingly, lens 1 as a whole can be controlled to provide adjustable optical effects for the beam 17, such as a round lens action of positive optical power or negative optical power in respect of a selectable optical axis, a cylinder lens action of positive optical power or negative optical power in respect of an adjustable plane of symmetry, a wedge prism action of adjustable power, but also actions which correspond to more complex optical elements.
A lens of the type shown in
Further lenses of variable optical power, which make use of a change in the shape of an interface for varying the optical power, are known from U.S. Pat. No. 6,369,954, CA 2,368,553 and U.S. Pat. No. 4,783,155, the full disclosures of which are incorporated herein by reference.
The principles of the present invention are applicable to arbitrary imaging optics, such as, for example, film cameras, photo cameras, telescopes, measuring optics or microscopes. As an example, a stereo-microscope will be described hereinbelow.
The objective 43 comprises a lens assembly 63 of a lens 64 of negative optical power, said lens being the lens of the objective 43 which faces the object plane 45. Furthermore, the lens assembly 63 comprises a lens 65 of positive optical power which is cemented with the lens 64.
The following Table 1 indicates three settings of the lenses 1a1 and 1a2 with focal lengths f1 and f2 caused by the controller 13a.
The setting No. 3 is shown in
This imaging optics thus operates like a Galilean telescope and has an afocal beam path on the entrance and exit sides. Both lenses 1a1 and 1a2 are oppositely controlled by the controller 13a, that is, proceeding from a magnification of 1.0× at which both lenses have an optical power of 0 dptr, the optical power of lens 1a1 is increased and the optical power of lens 1a2 is decreased in order to increase the magnification.
The curvature of the interface 33a between the two media 25a and 27a causes, apart from the optical power indicated in Table 1 which is indicated for a wave length of 546 nm in dptr, also a chromatic longitudinal aberration which is not negligible and is indicated in the following Table 2 in dptr (dioptre) for each one of the lenses 1a1 and 1a2 and for the total imaging optics 57a as optical power difference between blue light at 480 nm and red light at 644 nm:
It is evident from Table 2 that each one of the lenses 1a1 and 1a2 causes a considerable chromatic longitudinal aberration, but that the chromatic longitudinal aberration of the total optics 57a is considerably smaller than the chromatic longitudinal aberrations of the individual lenses. This is attributable to the fact that, due to the lenses 1a1 and 1a2 being oppositely controlled, their chromatic longitudinal aberrations are largely compensated in the zoom system 57a as a whole.
The zoom system 57a may replace the zoom systems 57 and 57′ of the conventional microscopy system described with reference to
Lenses 1b1 and 1b2 of variable optical power are again oppositely controllable by a controller (not shown in
Again, it is inferable from this table that the chromatic longitudinal aberration of the lenses 1b1 and 1b2 of variable optical power is relatively well compensated in the zoom optics 57b as a whole, due to these lenses being oppositely controlled.
Similar to Table 4 relating to the embodiment of
It is evident from Table 6 that the chromatic longitudinal aberrations in the optics 57c as a whole are relatively well compensated due to lenses 1c1 and 1c2 being oppositely controlled. A comparison of Table 6 with Table 4 shows that, in order to produce the same magnification 1.6×, 2.0× and 1.3×, smaller changes in the optical powers of the lenses 1c1 and 1c2 are necessary in the zoom optics 57c than in the embodiment described with reference to
The embodiments of the zoomable imaging optics described with reference to
The optics 57d comprises the following components disposed along a common optical axis 29d: a lens 1d1 of variable optical power, lenses 107d1 and 109d1 which are cemented together to form a lens assembly 105d1 of fixed positive optical power, lenses 107d2 and 109d2 which are cemented together to form a lens assembly 105d2 of fixed positive optical power, and a lens 1d2 of variable optical power. Again, a controller (not shown in
The following Table 7 indicates the optical data of the zoom optics 57d:
The following Table 8 indicates for three different settings of the magnification of the zoom optics 57d the optical powers of lenses 1d1 and 1d2, the change in the chromatic longitudinal aberration dependent on the control and how this chromatic longitudinal aberration is compensated in the zoom optics 57d as a whole:
It is evident from Table 8 that, due to the lenses of variable optical power being oppositely controlled, a nearly ideal compensation of the chromatic longitudinal aberration caused by the individual lenses is achieved.
Optical data of the zoomable microscope objective 43e are indicated in Table 9:
The objective 43e transforms an object-side beam bundle 47e, emanating from an object plane 45e, into an image-side beam bundle 49e having an afocal beam path. By controlling the lenses 1e1 and 1e2, it is possible to change both a working distance AA between the object plane 45e and the front lens 109e2 and the magnification generated by the objective 43e and the focal length thereof, respectively. In order to change the magnetization, at a given and held working distance AA, lenses 1d1 and 1e2 are oppositely controlled by the controller, that is, the optical power of one lens is increased and the optical power of the other lens is decreased.
The following Table 10 indicates six different settings of the control of lenses 1e1 and 1e2 for producing three different magnifications for each one of two different working distances:
Lenses 1f1, 1f2 are oppositely controllable by a controller (not shown in
Two further lens assemblies 105f1′ and 105f2′ are mounted on the support 115, said lens assemblies having a common optical axis 111′ enclosing an angle of 60° with the optical axis 111 of the lens assemblies 105f1 and 105f2. When the support 115 is rotated counter-clockwise by 60°, the lens assemblies 105f1 and 105f2 are removed from the beam path between the lenses 1f1 and 1f2 and the lens assemblies 105f1′ and 105f2′ are placed into the beam path between the lenses 1f1 and 1f2 such that the optical axis 111′ thereof coincides with the axis 29f. In this case, when the lenses 1f1 and 1f2 are controlled such that they provide no optical power, the optics 57f provides a basic magnification of 0.6×.
When the support 105 is further rotated counter-clockwise, the lens assemblies 105f1′ and 105f2′ are removed from the beam path between the lenses 1f1 and 1f2 and the beam path extends through openings 117 of the support 115 without a lens of fixed optical power being disposed in the beam path between the lenses 1f1 and 1f2. In this case, when the lenses 1f1 and 1f2 are controlled to provide no optical power, the optics 57f provides a basic magnification of 1.0×. When the support 115 is then further rotated counter-clockwise, the lens assemblies 105f1 and 105f2 are again placed into the beam path between the lenses 1f1 and 1f2. However, the lens assembly 105f2 is then at the top in
In each one of the above-described settings of the support 115, it is possible to oppositely control the lenses 1f1 and 1f2 in respect of their optical powers in order to vary the magnification provided by the optics 57 substantially continuously starting out from the basic magnification adjusted in each case. As the variation of the optical powers of lenses 1f1 and 1f2 is limited, the support 115 may then be rotated for a further variation of the magnification in order to provide another basic magnification by the lenses of fixed focal length.
The zoom optics 57f can be integrated into the microscopy system described with reference to
The above-described principles of the imaging optics of variable magnification provides a particularly efficient possibility to provide a product family with two groups of optical devices which differ from each other in that the devices of one group exhibit a zoom function and the devices of the other group do not exhibit a zoom function. The devices of both groups include optical components of fixed focal length which are substantially similar in structure. For example, the radii of curvature, the free diameters and vertex distances of a majority of the optical components of fixed focal length of the corresponding devices of both groups are substantially similar to each other. The devices of the zoomable group then comprise, as against the devices of the other group, at least two lenses of variable optical power which are inserted in the beam path spaced apart from one another. This enables to employ a common manufacturing process for the corresponding devices of both groups, which allows to provide the product group cost-efficiently.
For example, it is possible to employ the objective described with reference to
Equally, it is possible to use the zoom systems described with reference to
As is commonly known, spherical lenses whose thickness d on its optical axis accounts for much less than the difference of the radial r1 and r2 of its two surfaces can approximately be referred to as “thin lenses” whose optical power φDL and dispersion ηDL is directly proportional to the difference of the inverse radii, i.e., the curvatures k1 and k2 of their two surfaces. For assemblies of two of such thin lenses the following applies, likewise in approximation: the optical power φ of such an assembly is given by the sum of the optical powers φa and φb of the individual lenses, minus the product of the individual optical powers and the lens distance e:
φ≅φa+φb−e·φa·φb (1)
The dispersion η of such an assembly of two thin lenses is then given in approximation by the following equation:
η≅ηa+ηb−e·(ηa·φb+ηb·φa) (2)
Let's consider a system of four thin lenses which are disposed in pairs without a distance therebetween, one of the optical powers of the components of both pairs being fixed (φa,bf) and the other one variable (φa,bv). This results into a total optical power (e being the distance of the pairs) of:
φ≅(φaf+φav)+(φbf+φbv)−e·(φaf+φav)·(φbf+φbv) (3),
and correspondingly a total dispersion of
η≅(ηaf+ηav)+(ηbf+ηbv)−e·[(ηaf+ηav)·(φbf+φbv)+(ηbf+ηbv)·(φaf+φav)] (4)
Of particular importance is a simplified equation, in whose derivation it is presumed that the components of fixed focal lengths are configured such that their dispersion is negligible as compared to the dispersion of the components of variable optical power, i.e.:
η≅ηav+ηbv−e·[ηav·(φbf+φbv)+ηbv·(φaf+φav)] (5)
A further simplification is achievable for afocal systems, because in these systems the distance e of the lens pairs must be equal to the sum of the inverse optical powers:
It is inferable from this equation that a compensation of the total dispersion is achievable in an afocal system if the dispersion ηav and ηbv of the lenses of variable optical power and dispersion bear a ratio to each other which is determined by the squared ratio of the optical powers φa and φb, i.e., by the square of the imaging ratio Γ2, and only if ηav and ηbv have different preceding signs. Usually the latter case will occur if both lenses of variable optical power are oppositely controlled, i.e., if their optical powers φav and φbv have also different preceding signs. The variable optical powers to be set are given in an afocal system by the basic imaging ratio Γ0 and the imaging ratio ε to be adjusted in each case. Therefore, it is generally not possible or not practicable to achieve an exact compensation of the dispersion for all adjustable imaging ratios. It often suffices to provide such an exact compensation, except for the case that the lenses of variable optical powers are not controlled at all and thus do not provide any dispersion so that the system provides a basic imaging ration, for one further imaging ratio. It is found that, dependent upon the imaging ratio set, the residual dispersion describes a parabolic-type function which, provided that color-corrected components of fixed focal length are provided, intersects zero (corresponding to the negligible dispersion at the basic imaging ratio) and reaches relatively high positive values particularly for very large and very small imaging ratios. The vertex of the parabolic-type curve is near the basic imaging ratio if the optical power dispersion relations (Abbe values) of the two lenses of variable optical power are very similar, and are the more remote from the basic imaging ratio, and shifted towards negative dispersion, the more the Abbe values of the lenses differ from each other. By “negative dispersion” it is meant in the present context that the total optical power for blue light is less than for red light; if, therefore, an afocal system allowed a polychromatic beam bundle which enters the system in parallel to exit in parallel in respect of its green spectral portion, a blue spectral portion would exit the system divergently in case of a negative dispersion and a red spectral portion convergently. In a system with a finite intersection length, a “negative dispersion” means that the intersection length for blue light would be greater than the intersection length for red light.
The above derivation also comprises the case that the two components of fixed focal length have no optical power at all or are not present at all in that Zero is inserted for the respective optical powers and dispersions. It follows for this special case that an optimum dispersion compensation is achieved when the image ratio set corresponds to the ratio of the Abbe values of the lenses of variable optical power. If optically effective components of fixed focal length are present, an optimum dispersion compensation is achieved in similar way if the ratio which the imaging ratio set bears to the basic imaging ratio corresponds to the ratio of the Abbe values of the lenses of variable optical power. Between this imaging ratio given by said relationship and the basic imaging ratio, the residual dispersion is generally negative and varies only little with the adjusted imaging ratio set.
Actually, systems of variable optical power cannot exactly be considered as spaceless, so that every system comprising such lenses must be exactly calculated; the exact conditions for a minimum total dispersion of an imaging system with variable optical power differ in the individual case also for this reason more or less from the above-derived general regularities. Other reasons are a neglection of further substantial aberrations and the different demands made on the residual dispersion which is maximally tolerable for the individual application.
The above-discussed lenses of variable optical power may of course be substituted for by lens systems which each include a plurality of such lenses or which are composed of several ones of such lenses in order to achieve an even better dispersion compensation. For example, two different lenses which are oppositely controlled may be disposed closely one behind the other so that together they provide a considerable optical power, but only a little dispersion; the Abbe value of such a combination would thus be very high. With lenses of the type described with reference to
The only independently variable optical parameter of the lenses of the type shown in
As is evident from Tables 11 and 12, integrated lens systems of this type are preferably controlled such that the two interface curvatures bear a constant ratio to one another such that the displacement of the vertexes is always effected in the same direction. This requires an opposite change in the respective contact angle, i.e., also an opposite control. It is then achievable that the effective Abbe value of such a system remains largely independent of the optical power of the system. In this case, the above-indicated equation (6) is applicable again, according to which the total dispersion is dependent only on the individual dispersion and the adjusted optical powers of the components. Due to the chromatic aberration being in part already pre-compensated in the integrated systems, however, the effective Abbe values are in this case much higher than in case of an opposite curvature and can also have a negative preceding sign so that the resulting total dispersion can in the ideal case be kept tolerably small over the entire range of the envisaged imaging ratio.
In analogy to the zoom system shown in
Lens assemblies of the integrated type, even if they per se do not fully compensate the chromatic aberration, can also be combined to a zoom of the type shown in
If, however, the conical electrodes of an integrated lens system are synchronously controlled so that the displacement of the vertexes is effected oppositely, the pre-compensation of the chromatic aberration η is not that good, but the optical power φ is significantly higher (see Table 14). Due to the higher optical power of these lens systems, the overall length is relatively short. Therefore, such systems are suited better for afocal systems of the Keplerian type, as outlined in
In the objective system shown in
If the lenses of variable optical power are controlled such that the lens disposed rearwardly in the beam path has a positive optical power and the lens disposed in the front in the beam path has a negative, but in absolute terms a considerably higher optical power, the two lenses of variable optical power, due to their small distance as compared to the difference of their inverse optical powers, have the combined action of a component having a negative optical power (Equation 1). However, in correspondence with a relatively long objective focal length, the distance of the lens assemblies (see above) is larger than it corresponds to an afocal system, the optimal dispersion ratio regarding the chromatic aberration compensation must lie beyond the optimum value for an afocal system (ηavopt·φb/φa=−ηbvopt·φa/φb, see Equation 6):
e>1/φa+1/φb e>0 (7a)
φ>φa+φb φ>0 (because e·φa·φb<0) (7b)
|ηav/ηbv|opt>(φa/φb)2 (wherein |φa|>|φb|) (7c)
However, with simple lenses of variable optical power of the same structure only |ηav/ηbv|opt≈|φa/φb| is achievable. Therefore, the lenses of variable optical power should in such a case be composed differently or/and composed such that the above inequality is fulfilled.
If the lenses of variable optical power are controlled such that the lens disposed rearwardly in the beam path has a negative optical power and the front lens in the beam path has a positive, but in absolute terms, a higher optical power, the two lenses of variable optical power have the combined action, independent of their distance, of an element of positive optical power (see Equation 1) in correspondence with a relatively short objective focal length. As, in this case, the positive optical power of the lens assembly which is closer to the object already exceeds the negative contribution of the lens assembly which is more remote from the object and the distance-dependent term is likewise positive, an optimal chromatic aberration correction is again not achievable with simple lenses of variable optical power of the same structure (see Equation 2 with two positive terms because ηa+ηb>0). One possibility to compensate for chromatic aberrations consist in the selection of a higher dispersive lens of variable optical power for the lens assembly disposed more remote from the object and a low dispersive lens of variable optical power for lens assemblies disposed closer to the object. What is meant by high and low dispersive in the present case is that the dispersion is smaller and higher, respectively, at the same optical power, i.e., an effective Abbe value would be smaller and higher, respectively. Again, it is not possible to achieve a complete chromatic aberration compensation over the entire working distance and focal length range; however, except for the case where the lenses of variable optical power are not controlled, it is possible for a still further case, e.g., that of line 5 of Table 10 (working distance 300 mm, focal length 385), to obtain a compensation as optimal as possible, so that at the two working distances an about equally well chromatic aberration compensation is provided.
In principle, it is also possible for imaging purposes to use two-stage zoom optics, together with further lenses of fixed focal length, the total optical power of said zoom optics being negative in that the distance between two lens assemblies in said zoom systems is smaller than it corresponds to an afocal (Galilean) system, provided that the optical powers of the two lens assemblies have a different preceding sign, or is larger than it corresponds to an afocal (Keplerian) system, provided that the optical powers of the two lens assemblies have the same, namely positive, preceding sign. Of interest in this respect is particularly the first case, due to the shorter overall length, in which case the distance of the lens assembly is thus between Zero and the distance for an afocal system having the predetermined optical powers of the two lens assemblies (i.e., the sum of the inverse optical powers). Accordingly, the optimum value for the ratio of the individual dispersion lies between the value for a spaceless system (namely ηavopt=−ηbvopt; see Equation 2 with e=0) and the optimum value for an afocal system (Equation 6):
0<e<1/φa+1/φb (8a)
0>φ>φa+φb (8b)
1<|ηav/ηbv|opt<(φa/φb)2 (wherein |φa|>|φb|) (8c)
This applies, for example, to a case wherein an integrated system of the type shown in
Moreover, in these lens systems the dispersion is at least approximately proportional to the optical power, so that in each case an effective Abbe value ν=φ/η can be indicated which is even largely independent of the adjusted optical power and is determined only by the optical parameters of the liquids contained in the lens. On this condition, it follows from Equation 8c the optical value range in respect of the chromatic aberration compensation for the (amount)ratio of these Abbe values:
|φb/φa|<|νb/νa|opt<|φa/φb| (wherein |φa|>|φb|) (9a)
For systems with particularly small interface distances or, to be more exact, principal plane distances, the optimum is nearer to the lower limit, i.e.:
|φb/φa|<|νb/νa|opt<1 (wherein |φa|>|φb|) (9b)
Accordingly, for systems with particularly small differences in the optical power, or larger interface distances, the optimum is thus nearer to the upper limit, i.e.:
1<|νb/νa|opt<|φa/φb| (wherein |φa|>|φb|) (9c)
As in all other above-described examples, the optimum choice for the individual dispersions and Abbe values, respectively, is also dependent on the further aberrations, particularly spherical aberrations, which must also be compensated, and on the residual aberrations which is still tolerable in the respective application.
In the following, embodiments of the stereo-microscopy system according to the invention are described which make use of optical assemblies of variable optical action.
In the objective shown in
Equally, it is possible to dispose the lens of variable optical power on the surface of lens 64 which is not cemented with lens 65.
Optical data of both lenses 64 and 65 regarding materials, radii of curvature and vertex distances are indicated in Table 15 below. In this table, NSSK8 and NSF56 refer to glass materials which are obtainable from the company SCHOTT, Mainz, Germany.
Accordingly, an overall height of the lens assembly 63 is 10 mm, and a focal length of the two lenses 65 and 64 together is 205 mm, so that the focal length of the total lens assembly 63 consisting of lenses 64, 65, 66 is 205 mm if the lens 66 of variable optical power provides an optical power of 0 dptr.
a, 15b, 15c show beam paths of the object-side beam bundle 47k between the object plane 45k and the objective 43k for three different settings of the optical power of lens 66k. Moreover,
In the setting of
The optical data of the objective 43k in the three settings shown in
In the following, further variants of the embodiment described with reference to
The lens assembly 5812 comprises a lens 712 of negative optical power which is cemented with a lens 722 of positive optical power. A lens 732 of variable optical power is likewise disposed over the entire surface of the lens 712 which is not cemented with the lens 712. The lenses 731 and 732 of variable optical power are controlled by a controller 131 for controlling their optical powers to change the magnification of the zoom system 571.
a, 16b, and 16c show three different settings of the zoom system 571 for three different magnifications. Here, too, the lenses 731 and 732 are not shown as layers of constant thickness, but as corresponding lenses of glass which provide an optical power according to the respective setting.
The optical data of lenses 711, 721, 712 and 722 regarding materials, radii of curvature and vertex distances are indicated in Table 17 below. In said table, SF1, NSK4, NSK2 and NSF56, again, refer to glass materials which are obtainable from the company SCHOTT, Mainz, Germany.
Table 18 below indicates the values for the magnifications provided by the zoom system 571 in the three settings according to
The ocular 55m comprises a lens assembly 80 consisting of a lens 81 of negative optical power which faces the tube of the stereo-microscopy system and is cemented with a lens 82 of positive optical power, and a further lens of positive optical power 83 which has applied thereon over its entire surface a lens 84 of variable optical power. The lens 84 of variable optical power is controllable by a controller 13m to change the optical power of lens 84 thereof in order to compensate a vision defect of an eye viewing through the ocular 55m.
a, 17b, 17c show three different settings of the ocular 55m, the eye viewing through the ocular 55m being symbolically represented by an eye pupil AP and a lens 85 which symbolizes the vision defect. In
Optical data of the lenses 81, 82, 83 of the ocular 55m regarding materials, radii of curvature and vertex distances are evident from Table 19 below. Again, SF56A and SK55 refer to glass materials which are obtainable from the company SCHOTT, Mainz, Germany.
In
The controller 13m comprises a memory 87 for storing the characteristics of the three different settings of lens 84 shown in
The lens 66n of variable optical power is controlled dependent on the adjusted magnification in order to provide in the respective partial beam bundle 53n, 53′n an additional optical power, as it is represented in
The zoom systems 57n, 57′n are displaceable about the optical axis 42n of the objective 43n in circumferential direction, as intimated by arrow 93 in
The objectives 63o and 63′o are identical in structure with a lens 64o (64′o) of negative optical power, a lens 65o (65′o) of positive optical power and a lens 66o (66′o) of variable optical power, similar to the objective of the microscopy system described with reference to
Equally, the lens assembly 58p2 comprises a lens 71p2 of negative optical power which is cemented with lens 72p2 of positive optical power. The lens assemblies 58p1 and 85p2 are of identical structure and mirror-symmetrical in respect of a plane extending orthogonally to the optical axis 54p.
A further lens assembly 97 is disposed between the two lens assemblies 58p1 and 58p2, said lens assembly comprising two lenses 94 and 96 of positive optical power which are identical in shape and disposed likewise mirror-symmetrical in respect of a plane disposed between the two lenses 94, 96. A lens 95 of negative optical power is interposed in the space between the two lenses 94 and 96 and cemented with the two lenses 94 and 96. The lens assembly 97 is displaceable along the optical axis 54p by means of a drive 99 to change a magnification the zoom system 57e.
In contrast to the zoom system shown in
a, 20b, 20c show three different settings of the zoom system 57p for three different magnifications, the lens 73p of variable optical power being not depicted as layer of constant thickness, but as a corresponding glass lens which provides the corresponding optical power for the respective setting. The lens 73p of variable optical power and the motor 99 for displacing the lens assembly 97 along the optical axis 54p are controlled by a controller 13p which comprises a memory for storing the control values for the lens 73p of variable optical power and the motor 99 for the respective magnification values.
The optical data of lenses 71p1, 72p1, 96, 95, 72p2 regarding materials, radii of curvature and vertex distances are evident from Table 20 below. SF56A, SSK51, SF57, LSFN7, again, refer to glass materials which are obtainable from the company SCHOTT.
For the settings shown in
In contrast to the conventional zoom systems including two displaceable lens assemblies, the zoom system 57p shown in
In summary, objectives are proposed which comprise adjustable optical elements and, if desired, lenses of fixed focal length. By appropriately controlling the adjustable optical elements, the characteristics of the optics can thus be advantageously varied. To this end, systems are provided which are suitable for use as surgical stereo-microscope, objective, ocular and zoom, respectively.
A zoomable imaging optics according to the invention comprises lenses of variable optical power which, in order to change a magnification, can be oppositely controlled in the sense that the optical power of one lens is increased and the optical power of the other lens is decreased. In addition, the imaging optics may include further assemblies of fixed focal length.
While the invention has been described with respect to certain exemplary embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, the exemplary embodiments of the invention set forth herein are intended to be illustrative and not limiting in any way. Various changes may be made without departing from the spirit and scope of the present invention as defined in the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 103 49 293 | Oct 2003 | DE | national |
| 10 2004 026 580 | Jun 2004 | DE | national |
This application is a divisional application and thus claims benefit pursuant to 35 U.S.C. §120, of U.S. patent Application Ser. No. 12/170,864 filed on Jul. 10, 2008. Also, the parent application, U.S. patent application Ser. No. 12/170,864 is a divisional application and thus claims benefit pursuant to 35 U.S.C. §120, of U.S. patent application Ser. No. 11/408,633 filed on Apr. 21, 2006, now U.S. pat. No. 7,411,739, issued Aug. 12, 2008, which is a continuation application of PCT Application Number PCT/EP2004/012042, filed Oct. 25, 2004, which claims priority from German Patent Application No. 103 49 293.3 filed on Oct. 23, 2003 and German Patent Application No. 10 2004 026 580.1 filed on Jun. 1, 2004.
| Number | Name | Date | Kind |
|---|---|---|---|
| 4678899 | Baba et al. | Jul 1987 | A |
| 4784479 | Ikemori | Nov 1988 | A |
| 4871240 | Suda | Oct 1989 | A |
| 6459535 | Goto | Oct 2002 | B1 |
| 7443601 | Yoshida et al. | Oct 2008 | B2 |
| Number | Date | Country | |
|---|---|---|---|
| 20110063736 A1 | Mar 2011 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12170864 | Jul 2008 | US |
| Child | 12950402 | US | |
| Parent | 11408633 | Apr 2006 | US |
| Child | 12170864 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/EP2004/012042 | Oct 2004 | US |
| Child | 11408633 | US |
