Classifications

• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B15/00—Optical objectives with means for varying the magnification
  • G02B15/14—Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective
  • G02B15/22—Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective with movable lens means specially adapted for focusing at close distances
  • G02B15/24—Optical objectives with means for varying the magnification by axial movement of one or more lenses or groups of lenses relative to the image plane for continuously varying the equivalent focal length of the objective with movable lens means specially adapted for focusing at close distances having a front fixed lens or lens group and two movable lenses or lens groups in front of a fixed lens or lens group
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B13/00—Optical objectives specially designed for the purposes specified below
  • G02B13/04—Reversed telephoto objectives
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B13/00—Optical objectives specially designed for the purposes specified below
  • G02B13/18—Optical objectives specially designed for the purposes specified below with lenses having one or more non-spherical faces, e.g. for reducing geometrical aberration
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
  • G02B27/0075—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00 with means for altering, e.g. increasing, the depth of field or depth of focus
• • G—PHYSICS
  • G02—OPTICS
  • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
  • G02B9/00—Optical objectives characterised both by the number of the components and their arrangements according to their sign, i.e. + or -
  • G02B9/60—Optical objectives characterised both by the number of the components and their arrangements according to their sign, i.e. + or - having five components only

Definitions

• the invention relates to a replaceable fixed focal length lens according to the preamble of claim 1.
• Such lenses are known for photographic imaging purposes from analog photography and are also used for digital image capture. Increasingly, digital cameras no longer have one in the image recording beam path and
• the image selection is carried out by permanent image acquisition with the image sensor and based on an obtained on a display on the back of the camera object section or with the help of a
• photographic objectives for producing a good imaging performance consist of two or more lens groups, which in turn are mounted so as to be stationary or displaceable along the optical axis
• Optical aberrations such as distortion, field curvature, aperture aberration, chromatic aberration and coma increase. The image results are then no longer sufficient despite the focus on the desired object distance
• Focal length change and independently of this another lens group is used for focusing.
• Such a variable focal length objective is known, for example, from US 2013/0070124 A1.
• This lens has three movable lens groups for focal length and focus change.
• Front lens group follows an axially adjustable lens group for zooming. Between two other fixed ones
• Lens groups are two independently adjustable
• Inserted focusing lens groups With the help of the two focusing lens groups, aberrations arising as a function of the focal length change are to be compensated.
• the invention was based on the object, interchangeable
• Fixed focal length lenses allow a very high constant image quality when focusing on different object distances from infinity to the extreme near range below 30 cm or with a magnification of up to 1: 3, where the
• Focusing needed lenses should have a simple lightweight construction, to get a fast and quiet
• the lenses should be suitable for use on mirrorless recording systems with short Auflageteil, have a short focal length and at the same time a sufficiently large distance between the exit pupil of the lens and the
• automatic correction programs such as "Code V” from Optical Research Associates, are used, which are able to calculate suggested lens sequences and refractive power distributions suggestions for functional objective systems with a correction state optimized for a particular task due to targeted changes of the given parameters by the
• the essential solution feature of lenses according to the invention is to provide two focusing lens groups slidably mounted along an optical axis with respect to an imaging plane in a lens barrel, with a focus front group viewed from the object side and a focus behind group as seen from the object side behind a fixed one
• Middle group with lenses and aperture are arranged.
• the path of the aberrations introduced when focusing on different object distances is advantageously compensated for one another.
• an objective according to the invention has a fixed front view seen from the object side and a fixed rear lens group facing the imaging plane. In this way, a lens of fixed focal length is realized, which consists of five lens group, of which three are fixed and two slidably mounted for focusing purposes along the optical axis.
• the two focusing lens groups together shift the focal position to focus the object plane on the imaging plane.
• the front lens group and the rear lens group have negative refractive power, or the front lens group and the rear lens group have positive refractive power.
• the front lens group have positive power and the rear lens group negative refractive power or the front lens group negative and the rear lens group positive refractive power.
• both the focusing front group G2 and the focusing background group G4 have positive refractive power and move away from the imaging plane IM when focusing from infinity to near-focus.
• Focusing from infinity to near-focus approximates the imaging plane.
• both the focusing front group G2 and the focusing rear group G4 approach when focusing from infinity into the close-up of the
• Imaging plane IM where both focusing groups have negative refractive power.
• the focusing front group G2 has negative and
• the front lens group having a positive overall refractive power.
• Total refractive power ensures a favorable distribution of the refractive powers in the rear assembly and compliance with structural requirements, for example, from the given
• Lens diameter has, if the optical imaging performance
• the open-face number usually decreases with the same or worse imaging performance of the design effort.
• a scaling of the geometric data of the lens to other image formats is possible while maintaining the respective aperture number and causes a corresponding scaling of the focal length. In this way realized lenses, with otherwise respect to the
• Lens are the ratio f1 / f of the focal lengths f1 of
• ratio f1 / f is absolute to the top (large amounts).
• An embodiment of the invention optimized in terms of assembly tolerances and size therefore has a ratio f1 / f of -1, 7 and -1, 0 or intermediate values or of 0.5 and 2, 1 or intermediate values.
• Focusing front group and the length of the lens can be achieved by restricting the ratio f2 / f to a range between -1, 0 and -0.3 or between 1, 0 and 10.0.
• small focusing strokes are advantageous for fast focusing, but they also increase tolerance sensitivity.
• an excessive focusing stroke increases the overall length and, on the other hand, requires powerful and fast motor drives with high energy consumption for focusing.
• Double focussing according to the invention is therefore the restriction of the ratio f2 / f to -0.7 and -0.4 or 1, 3 and 5.6, or a range between one of the two aforementioned ranges particularly advantageous.
• An advantageous optimization carried out in the same way for the focusing background group is shown by a restriction of the
• Ratio f4 / f to a range between -5.0 and 5.0 with further optimization by a restriction to -1, 9 and -0.8 or to 0.6 and 0.9, or an area between - 1, 9 and -0.8 or between 0.6 and 0.9.
• An advantageous embodiment of the lenses of the middle group in terms of manufacturing tolerances and size is achieved by restricting the ratio f3 / f to a range between -2.0 and -0.5 or 0.2 and 5.0, wherein an inventive optimization in a Ratio f3 / f of -1, 2 and -1, 0 or 0.4 and 3.4, or in a range between -1, 2 and -1, 0 or between 0.4 and 3.4.
• Rear lens group results in an unfavorably large length, in small amounts, the lens group is sensitive to mounting tolerances.
• An advantageous optimization therefore consists in limiting the ratio f5 / f to a range between -28.0 and -0.6 or between 0.5 and 10.0.
• the lenses are thus suitable for camera systems with a short support dimension and short cutting distance, e.g. each smaller 25mm, based on the small picture format described above, particularly suitable. Too small values of the ratio f5 / f therefore have an unfavorable effect, since they increase the angle of incidence of light and thus increase the vignetting.
• An embodiment of the objective optimized with regard to this problem therefore has values for the ratio f5 / f of -21, 0 and -0.8 or 0.8 and 5.2, or a value in each case in the region between them.
• the objective has a ratio of the total focal length f to the image circle diameter in the imaging plane (IM) between 0.3 and 5. In this way, you can lenses with a sufficiently large distance between the exit pupil and the imaging plane, eg greater than 40mm, and with a focal length between 13mm and 216.5mm, based on the small format described above, realize.
• Focusing front and focusing backgroup to the image circle diameter in the image plane is smaller than the third power
• the respective focusing group has a weight of less than 10 g (grams).
• the value for the relative volume of 0.08 then corresponds, in terms of the 35 mm format, to a light glass, such as for example N-PSK53A from Schott, a weight of 23.2 g and for a heavy glass, such as N, for example -LASF31A from Schott, a weight of 35.8 g.
• a light glass such as for example N-PSK53A from Schott
• a heavy glass such as N, for example -LASF31A from Schott, a weight of 35.8 g.
• For medium-format systems with a magnification of 1.5 times the image circle diameter this results in lens weights of 78.3 g for a light glass and 120.8 g for a heavy glass.
• APS systems with a 1.5x smaller image circle diameter this results in lens weights of 6.9 g for a light glass or 10.6 g for
• the front lens group of four lens members wherein the first lens member, the second lens member and the third lens member positive and the fourth lens member have negative refractive power, wherein the third lens member and the fourth lens member to a
• Front lens group is as a lens 1: 2 90mm and 1: 2 75 in Fig. 1 and 2 is shown in more detail on the basis of the assigned tables with focal length data [f] and refractive power values [Dpt.].
• the front lens group consists in an alternative lens of four lens members, wherein the first lens member and the second lens member positive, the third lens member negative and the fourth lens member has positive refractive power, wherein either the third lens member and the fourth lens member to a lens doublet with negative
• Exemplary embodiments which are as 1: 2 90mm lenses based on the associated tables with focal length data [f] and
• the front lens group also consists of four lens members, wherein the first lens member and the second lens member has negative, the third lens member positive and the fourth lens member negative refractive power.
• the third and fourth lens elements are combined into a lens doublet with negative total power.
• a 1: 2.0 24mm lens with exact group focal lengths and power values is given in Fig. 5 with associated table.
• the front lens group assists in another lens of only one lens member having negative or positive refractive power.
• Fig. 4 shows a 1: 2.0 50mm and Fig. 8 a 1: 1, 4 50mm objective and more accurate values with the respective tables.
• the front lens group consists of two lens elements, the first lens element having positive and the second lens element having negative refractive power and both having a lens doublet with a negative lens
• FIG. 9 of the drawing shows a corresponding embodiment, which is described in more detail as a 1: 1, 4 50mm lens based on the associated table.
• the front lens group consists of three lens elements, the first lens element and the second lens element being negative and the third
• Lens member has positive refractive power.
• the second and the third lens element are thereby a lens doublet with negative
• the middle group consists of a lens element of positive refractive power, wherein the iris diaphragm AP is arranged stationarily in front of it.
• this consists of two lens elements, the first lens element having negative and the second lens element having positive refractive power, and the iris diaphragm AP being arranged in a stationary manner between the first and the second lens element.
• Figures 1 and 2 show such a middle group.
• this consists of three lens members, wherein the first lens member is negative, the second lens member positive and the third lens member positive Refractive power has.
• the first and the second lens member are combined to form a lens doublet having a positive overall refractive power, and the iris diaphragm AP is arranged in a fixed manner in an example shown in FIG. 5 between the lens doublet and the third lens member.
• the iris diaphragm AP is arranged in a stationary manner in front of the first lens member.
• the middle group consists of four lens members, wherein the first lens member positive, the second negative, the third and the fourth lens member has positive refractive power.
• the second and the third lens element are combined to form a lens doublet having a positive overall refractive power, wherein the iris diaphragm AP is arranged in a stationary manner in front of the first lens element.
• FIG. 3 shows such an exemplary embodiment.
• FIG. 4 shows an embodiment with a middle group consisting of five lens elements.
• the first lens member has positive and the second lens member negative refractive power, both are a lens doublet with negative overall power
• Lens member negative and the fourth lens member positive refractive power, wherein both are combined into a lens doublet with positive overall power.
• the fifth lens member has positive refractive power and the iris diaphragm AP is stationary between the two
• the middle group consists of six lens members, wherein the first lens member positive and the second lens member negative refractive power and both are combined to form a first Linsenduplett with negative overall power.
• the third lens element has positive, the fourth lens element negative and the fifth lens element positive refractive power, wherein the fourth and fifth lens element combined to form a second lens doublet with negative total refractive power.
• Lens member has positive refractive power.
• the iris diaphragm AP is arranged in a stationary manner between the first lens doublet and the third lens member.
• the rear lens group consists of three lens members, wherein the first lens member positive and the second lens member negative refractive power and both are combined to form a Linsenduplett with negative total refractive power.
• the third lens element has a negative refractive power in an embodiment shown in FIGS. 8 and 9.
• Rear lens group also of three lens members, wherein the first lens member positive and the second lens member negative refractive power and both to a lens doublet with positive
• the third lens element has positive refractive power.
• An alternative embodiment has a rear lens group with two lens members. Those shown in Figures 1, 2 and 7
• Embodiments have positive refractive power in the first lens element and negative refractive power in the second lens element, respectively.
• a rear lens group composed of only one lens element of negative refractive power is shown by way of example in FIGS. 4, 5 and 6.
• lens elements particularly advantageous for correcting monochromatic aberrations, such as opening defects, coma, astigmatism, curvature and distortion one or more lens elements, be provided with one or two aspherical surfaces.
• Cutting distance e.g., less than 25mm, based on the 35mm format
• location of the exit pupil suitable for imaging sensors
• the rear lens groups can have at least one lens with an optical material with refractive index ne greater than 1, 8.
• limitations can also be imposed on the maximum diameters of the lenses due to predetermined limiting diameters given by the camera or imaging system, e.g. a bayonet.
• the individually shown and described five lens groups represent in all lens variants a necessary in each case, self-contained component.
• Each of the lens groups can be optically tuned for themselves, which in particular by the specified for each lens group focal length ratio
• 1 is a lens section through a lens with the focal length 90mm and aperture number 2
• Fig. 4 shows a lens section through a lens with the focal length 50mm and aperture number 2
• FIG. 10 shows an image sensor in an imaging plane IM.
• Horizontal lines represent the positions of the lens groups G1, G2, G3, G4, and G5.
• the upper of these lines indicate the positions in the infinity focus setting, the lower ones in the focus setting to the shortest object distance, and the middle ones in the middle focus setting.
• the vertical lines are associated with the stationary lens groups G1, G3 and G5, the oblique lines with the shiftable focusing groups G2 and G4.
• the lens cuts in the drawing are drawn to scale so that relative indications, such as those shown in FIG. in Fig. 1 at the lens member
• Lens group G1 from a seen in the light direction to the imaging plane IM sequence of second, with approximately the thickness of the first lens G1 L1 spaced convex-concave lenses of positive refractive power is constructed, which is associated with a cemented cement with a smaller distance below, which consists of a biconvex lens more positive and

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• Optics & Photonics (AREA)
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• Nonlinear Science (AREA)

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