JP2019074654A - Zoom lens manufacturing method and zoom lens system - Google Patents

Abstract

To identify a lens of a replacement object suitable for correcting a magnification chromatic aberration.SOLUTION: A method of manufacturing a zoom lens system is provided that is configured to: obtain a magnification chromatic aberration of a substantive zoom lens system; and replace at least one lens to be included in a zoom lens system on a design due to the obtained magnification chromatic aberration. In the replacement, a lens group serving an object is present that does not move during zooming and moves along an optical axis upon focusing, and the lens group serving the object does not includes a lens on a contraction side end of the zoom lens system, and a lens on an enlargement side end thereof. When the lens group serving the object includes a first bonding lens, the first bonding lens is exchanged with a bonding lens in which a radius of curvature of a surface on the enlargement side and a radius of curvature of a surface on the contraction side are the same, and a radius of curvature of a bonding surface is different.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method of manufacturing a zoom lens system.

  Patent Document 1 describes a method of manufacturing an optical system having a lens system including a plurality of lenses, wherein assembling the optical system, acquiring a chromatic aberration of the optical system by performing a performance test, and Due to the chromatic aberration, the optical distances of the optical elements inserted between the plurality of lenses, either outside the lens on the most enlargement side of the plurality of lenses or outside the lens on the most reduction side of the plurality of lenses are the same And replacing with another optical element having a different chromatic aberration of magnification.

International Publication WO2015 / 004926

  In this manufacturing method, it is not easy to select an optical element to be replaced within a range that does not affect the performance of the lens system such as other aberration correction performance as much as possible.

One aspect of the present invention is a method of manufacturing a zoom lens system, comprising the following steps.
1. To obtain the chromatic aberration of magnification of a real zoom lens system.
2. Replacing at least one lens included in the designed zoom lens system by the obtained magnification chromatic aberration. In this process, there is an objective lens group that does not move during zooming but moves along the optical axis during focusing, and the objective lens group is the lens at the reduction end of the zoom lens system and the enlargement side If the target lens group includes the first cemented lens, the radius of curvature of the surface on the enlargement side and the radius of curvature of the surface on the reduction side are the same. , And replacing the cemented lens with a different radius of curvature of the cemented surface.

  In the zoom lens system, lenses that do not move during zooming do not have much effect on zooming performance even if they are replaced. Furthermore, a cemented lens is included in the objective lens group that moves along the optical axis during focusing and meets the condition that does not include the lens at the reduction end and the lens at the enlargement end. If so, the cemented lens (first cemented lens) is a chief ray, for example, if it is a zoom lens system for projection, a chief ray emitted from the end of the light modulation device, a zoom lens system for imaging In this case, the chief ray incident on the end of the imaging device forms a relatively parallel light, for example, 5 degrees or less, preferably 3 degrees or less, at a relatively small angle with the optical axis when passing through the cemented surface. Therefore, it is possible to suppress the influence on the other aberration correction performance by replacing the cemented lens with a different curvature radius of the cemented surface.

  One of the other aspects of the present invention is a zoom lens system having a target lens group that does not move during zooming but moves along an optical axis during focusing, and the target lens group is The radius of curvature of the surface on the magnification side and the radius of curvature of the surface on the reduction side due to the chromatic aberration of magnification of the zoom lens system of the entity at manufacture, not including the lens on the reduction side and the lens on the enlargement side of the zoom lens system Is a zoom lens system including a first cemented lens to be replaced with a cemented lens having the same curvature radius of cemented surface. The zoom lens system may be a zoom lens system for projection, and a projector having the zoom lens system and a light modulation device disposed on the reduction side of the zoom lens system is also included in the scope of the present invention. In addition, the zoom lens system may be a zoom lens system for imaging, and an imaging apparatus having the zoom lens system and an imaging device disposed on the reduction side of the zoom lens system is also included in the scope of the present invention.

5 is a flowchart illustrating a method of manufacturing a zoom lens system. The figure which shows an example of a zoom lens system. FIG. 3 (a) shows lens data, FIG. 3 (b) shows zoom data, and FIG. 3 (c) shows aspheric surface data. FIG. 4A is a view showing a design value at the wide-angle end, and FIG. 4B is a view showing a design value at the telephoto end. FIG. 5A is a view showing an actual measurement value at the wide-angle end, and FIG. 5B is an actual measurement value at the telephoto end in the reference state. FIG. 6 (a) shows the measured value at the wide-angle end, and FIG. 6 (b) shows the measured value at the telephoto end after the cemented lens is replaced, in the zoom lens system. FIG. 7A is a view showing an actual measurement value at the wide-angle end, and FIG. 7B is an actual measurement value at the telephoto end in another example of magnification chromatic aberration of the zoom lens system in the reference state. FIG. 8A is a view showing an actual measurement value at the wide-angle end, and FIG. 8B is an actual measurement value at the telephoto end after replacing the cemented lens; The figure which shows the different example of a zoom lens system. FIG. 10 shows various values of the zoom lens system shown in FIG. 9, FIG. 10 (a) shows lens data, FIG. 10 (b) shows zoom data, and FIG. 10 (c) shows aspheric data. FIG. 11 is a diagram showing design values of magnification chromatic aberration of the zoom lens system shown in FIG. 9, FIG. 11 (a) shows design values at the wide angle end, and FIG. 11 (b) shows design values at the telephoto end. FIG. 12A is a view showing an actual measurement value at the wide-angle end, and FIG. 12B is an actual measurement value at the telephoto end in the reference state. FIG. 13A is a view showing an actual measurement value at the wide-angle end, and FIG. 13B is an actual measurement value at the telephoto end after replacing the cemented lens; FIG. 14A is a view showing an actual measurement value at the wide-angle end, and FIG. 14B is an actual measurement value at the telephoto end according to another example of the magnification chromatic aberration of the zoom lens system in the reference state. FIG. 15A is a view showing an actual measurement value at the wide-angle end, and FIG. 15B is an actual measurement value at the telephoto end after replacing the cemented lens;

  FIG. 1 shows a method of manufacturing a zoom lens system according to the present invention. In step 51, it is confirmed whether the configuration of the zoom lens system includes a cemented lens to be replaced (replacement target). The zoom lens system includes a target lens group that does not move during zooming but moves along the optical axis during focusing, and the target lens group is a lens at the end of the zoom lens system on the reduction side If the cemented lens is not included, and the cemented lens is included, the curvature radius of the surface on the enlargement side and the curvature radius of the surface on the reduction side are the same, and the curvature of the cemented surface is the same. It can be set as the 1st junction lens (junction lens of substitution object) which can be replaced by the junction lens from which a radius differs.

  In a zoom lens system that includes a cemented lens to be replaced, step 52 obtains the chromatic aberration of magnification of an actual zoom lens system that includes a lens made of a material that is manufactured or actually used.

  The first typical method for obtaining the magnification chromatic aberration of a solid zoom lens system is to create individual optical elements constituting a zoom lens system based on a real glass material, as shown in the design drawing of a real zoom lens system The zoom lens system is assembled to actually measure the chromatic aberration of magnification of the finished zoom lens system. According to this method, since the zoom lens system is actually measured by a measuring instrument to measure the magnification chromatic aberration, it is possible to obtain the magnification chromatic aberration of the real zoom lens system with high accuracy, and in each zoom lens system It is possible to measure lateral chromatic aberration including the tolerance variation of each lens. Therefore, it is a preferred method to make a more appropriate correction in the subsequent steps.

  The second method is to obtain the chromatic aberration of magnification of the actual zoom lens system by simulation. In order to manufacture each lens of the zoom lens system of an entity for glass material data (ideal value of refractive index at each wavelength) of each glass material designated for each optical element on design data of the zoom lens system Obtained by redesigning the zoom lens system by reflecting on the design data the glass material data (measured values of the refractive index at each wavelength) obtained by actually measuring (measuring) the actual glass materials purchased. The chromatic aberration of magnification can be measured by simulating and analyzing the chromatic aberration of magnification based on the design data of the zoom lens system after the redesign. According to this method, it is only the glass material data that requires actual measurement data, so it is not necessary to create an optical element based on an actual glass material or assemble a zoom lens system based on the created optical element. The chromatic aberration of magnification of the zoom lens system can be determined, and the time required for the correction can be shortened and the cost for trial manufacture can be reduced.

  Hereinafter, the present invention will be described by taking the first method as an example. That is, in the following, the actual measurement image may be an image actually measured by the first method, or may be an image obtained by simulation by the second method. The chromatic aberration of magnification is a second actual image size (second image) of a second wavelength shorter than the first wavelength, based on the actual image size of the first wavelength (the actual image size of the first wavelength). Acquisition of the second measurement image size of 2 wavelengths and the third measurement image size of the third wavelength (third measurement image size of the third wavelength) longer than the first wavelength can do. An example of the first wavelength is e-line (wavelength 587.6 nm) using mercury as a light source, and an example of the second wavelength is g-line (wavelength 435.8 nm) using mercury as a light source, and An example of the wavelength of is C line (wavelength 656.3 nm) which uses hydrogen as a light source. The measurement results are based on the image size of the g-line (second measurement image size) obtained by measurement and the image size of the C-line (third measurement image size) based on the measurement image size of the e-line with respect to the image height. That is, the image size of the e-line can be expressed as a reference line (straight line) along the image height and a value (curve) shifted with respect to it in the plus or minus direction.

  The actual measurement results are compared to reference values calculated based on the specifications of the zoom lens system in the following steps 53 and 55. The reference value of the designed zoom lens system is the second wavelength (g-line) based on the image size of the first wavelength (e-line) calculated based on the specifications of the zoom lens system as well as the measurement result. And the third reference image size of the third wavelength (C-line), and the image size of the e-line is added as a reference line (straight line) along the image height Or it can be expressed as a value (curve) shifted in the negative direction.

  In step 53, the measured image size (second measured image size) of the g line based on the e line is shifted to the negative side with respect to the reference image size (the second reference image size), or the e line When the measured image size of the C line (third measured image size) on the basis of is shifted to the positive side with respect to the reference image size (third reference image size), the g line image size is set to the positive side Or move the C-line image size to the negative side. Therefore, in step 54, the first cemented lens to be replaced (replacement target) inserted in the zoom lens system when the measurement result is obtained is replaced (replaced) with a cemented lens having a large curvature radius of the cemented surface. Do.

  On the other hand, in step 55, the measured image size (second measured image size) of the g-line with the e-line as a reference is shifted to the positive side with respect to the reference image size (second reference image size) If the measured image size of the C-line (third measured image size) based on the e-line is shifted to the negative side with respect to the reference image size (third reference image size), the g-line image size is It is necessary to move to the negative side or to move the image size of the C line to the positive side. Therefore, in step 56, the first cemented lens to be replaced, which is inserted in the zoom lens system when the measurement result is obtained, is replaced with a cemented lens having a small curvature radius of the cemented surface.

  An example of the projector 1 provided with the zoom lens system 10 is shown in FIG. The projector 1 includes a light modulation device (light valve) 5 disposed on the reduction side 2 of the zoom lens system 10, and the image light (projected light) formed by the light valve 5 is transmitted to the enlargement side of the zoom lens system 10. Enlarge and project to the screen 6 of 3 etc. The zoom lens system 10 can also be applied to an imaging device. In the case of an imaging device, an imaging device (imaging element) is installed on the reduction side 2 of the zoom lens system 10.

  The projector 1 may be a front projector or a rear projector including a screen. One example of the light valve 5 is a DMD (digital microphone port mirror device), and may be a device that forms other images such as a reflective LCD, a transmissive LCD, LCoS, or an organic EL. The light valve 5 may be of a light emitting type, and may be of an illumination type including a lighting device. The screen 6 may be a whiteboard, a wall surface, or a table surface.

  This lens system (optical system, optical device, optical system) 10 is a six-group configuration including a first lens group G1 to a sixth lens group G6 arranged in order from the enlargement side 3, and has 16 lenses The zoom lens system 10 includes the third lens group G3 and the fourth lens when zooming from the wide angle end (WIDE) shown in FIG. 2A to the telephoto end (TELE) in FIG. 2B. The group G4 and the fifth lens group G5 move to the enlargement side 3. On the other hand, the first lens group G1, the second lens group G2, and the sixth lens group G6 do not move during zooming, and the first lens group G1 and the second lens group G2 do not move during focusing. Move to Furthermore, the second lens group G2 includes a cemented lens LB1.

  Therefore, the second lens group G2 of the lens system 10 is a target lens group that does not move during zooming but moves along the optical axis 7 during focusing. Further, the second lens group G2 does not include the lens at the end of the reduction side 2 and the lens at the end of the enlargement side 3 of the zoom lens system 10, and includes the cemented lens LB1. Therefore, in the zoom lens system 10, as the cemented lens (first cemented lens) to be replaced, the cemented lens LB1 can be replaced with a lens having a different curvature radius of the cemented surface SS to correct magnification chromatic aberration. It can be set (step 51).

  The configuration of the zoom lens system 10 will be described in more detail. The first lens group G1 on the most enlargement side 3 is a fixed lens group that has a negative refractive power as a whole and does not move during zooming, and moves the focus from near distance to long distance during focusing. Move to the enlargement side 3. The first lens group G1 includes, in order from the enlargement side 3, a positive meniscus lens L1 convex on the enlargement side 3, a negative meniscus lens L2 convex on the enlargement side, and a biconcave negative lens L3.

  The second lens group G2 is a fixed lens group that has a positive refractive power as a whole and does not move during zooming. When focusing, the second lens group G2 moves the focus from a near distance to a far distance. Move to The second lens group G2 is a biconcave negative lens in total from the enlargement side 3 and includes a cemented doublet lens (balsam lens) LB1 and a biconvex positive lens L6. The cemented lens LB1 includes a biconcave negative lens L4 and a positive meniscus lens L5 convex on the enlargement side 3.

  The third lens group G3 has a positive refractive power as a whole, and is a moving lens group that moves during zooming, and does not move during focusing. The third lens group G3 includes a biconvex positive lens L7.

  The fourth lens group G4 is a moving lens group that has a positive refractive power as a whole and moves with the stop St disposed on the enlargement side 3 during zooming, and does not move during focusing. The fourth lens group G <b> 4 includes a cemented doublet lens LB <b> 2 of positive meniscus type convex on the reduction side 2. The cemented lens LB2 includes a positive meniscus lens L8 convex on the reduction side 2, a negative meniscus lens L9 convex on the reduction side 2, and a positive meniscus lens L10 convex on the reduction side 2.

  The fifth lens group G5 is a moving lens group that has a positive refractive power as a whole and moves during zooming, and does not move during focusing. The fifth lens group G5 includes, in order from the enlargement side 3, a cemented doublet lens LB3 of positive meniscus type convex to the reduction side 2 and two sheets of negative meniscus type convex to the reduction side 2 And a biconvex positive lens L15. The cemented lens LB3 includes a biconcave negative lens L11 and a biconvex positive lens L12. The cemented lens LB4 includes a biconcave negative lens L13 and a biconvex positive lens L14.

  The sixth lens group G6 on the most reduction side 2 is a fixed lens group that has a positive refractive power as a whole and does not move during zooming, and does not move during focusing. The sixth lens group G6 includes a positive meniscus lens L16 convex on the enlargement side 3.

  The numerical values of the zoom lens system 10 are shown in FIG. 3A shows lens data of the lens system 10, FIG. 3B shows zoom data of the lens system 10, and FIG. 3C shows aspheric surface data of the lens system 10. In FIG. 3A, the radius of curvature Ri (mm) of each surface (S) of each element (each lens surface in the case of a lens) arranged in order from the screen 6 side, each element arranged in order from the screen 6 side Shows the distance di (mm) between the faces of each element, the effective diameter H * 2 (diameter, mm) of each element, the refractive index nd (d line), the Abbe number d d (d line), and INF is infinite (plane) And IMG shows an image.

The surface S6 of the negative meniscus lens L3 of the first lens group G1 is aspheric, and X is a coordinate in the direction of the optical axis 7, Y is a coordinate in the direction perpendicular to the optical axis 7, and the traveling direction of the light is aspheric Assuming that R0 is a paraxial radius of curvature, it is expressed by the following equation using coefficients K, A, B, C and D in FIG. 3 (b). "En" means "10 to the n-th power". The same applies to the following embodiments.
X = (1 / R0) Y 2 / [1+ {1- (1 + K) (1 / R0) 2 Y 2} 1/2]
+ AY ⁴ + BY ⁶ + CY ⁸ + DY ¹⁰

  FIG. 4 shows design values (reference values, reference data) of magnification chromatic aberration calculated based on the specifications of the zoom lens system 10. FIG. 4 (a) is a design value of magnification chromatic aberration at the wide angle end, and FIG. 4 (b) is a design value of magnification chromatic aberration at the telephoto end. The magnification chromatic aberration in FIGS. 4A and 4B is based on the image size of the e-line (first wavelength, wavelength 587.6 nm, solid line), and the g-line (second wavelength, wavelength 435. The image size (second reference image size) of 8 nm, one-dot chain line) is shown along the image height, and the image size (third reference) of the long wavelength c-line (third wavelength, wavelength 656.3 nm, broken line) Image size) is shown along the image height.

  The glass material employed for the lens of the zoom lens system 10 has ideal values of refractive index and Abbe number, and the design is performed based on the ideal value. However, although the glass material actually received is within the tolerance range, the numerical values are shifted, and the optical performance of the zoom lens system 10 is compared with the designed value due to the deviation of the numerical values. But within the range of The most susceptible aberration is lateral chromatic aberration. The performance required of the projection optical system is increasing as the definition and angle of the projector are advanced. Therefore, it is required to correct the lateral chromatic aberration even if the lateral chromatic aberration is caused by the deviation of the refractive index and the Abbe number within the tolerance range of each glass material. The same applies to a zoom lens system for imaging.

  FIG. 5 shows an example of lateral chromatic aberration measured in the lens system 10 in a state (reference state) assembled based on the lens data shown in FIG. 3 (step 52). FIG. 5 (a) is an actual measurement value of lateral chromatic aberration at the wide angle end, and FIG. 5 (b) is an actual measurement value of lateral chromatic aberration at the telephoto end. In each actual measurement value, the measured g-line (second wavelength, wavelength 435.8 nm, one-dot chain line) is measured based on the measured image size of e-line (first wavelength, wavelength 587.6 nm, solid line) Image size (second measured image size) along the image height, and the measured image size of the c-line (third wavelength, wavelength 656.3 nm, broken line) (third measured image size) Shown along the high. The radius of curvature of the cementing surface SS of the cemented lens LB1 to be replaced in this figure is 47.52 mm, which is the reference radius.

  It can be seen that the measured image size of the second wavelength, the g-line, is shifted to the negative side at both the wide angle end and the telephoto end, as compared with the reference image size shown in FIG. Therefore, based on step 53, in step 54, the cemented lens LB1 to be replaced is replaced with a lens having a large radius of curvature of the cemented surface SS.

  FIG. 6 shows measured values when the cemented lens LB1 is replaced with a cemented lens in which the radius of curvature of the cemented surface SS is 48.52 mm. As shown at the wide-angle end (FIG. 6A) and at the telephoto end (FIG. 6B), it can be seen that lateral chromatic aberration is corrected to a state close to the reference state.

  FIG. 7 shows an example of lateral chromatic aberration measured in another lens system 10 in a state (reference state) assembled based on the lens data shown in FIG. 3 (step 52). At the wide-angle end (FIG. 7 (a)) and the telephoto end (FIG. 7 (b)), the measured image size of the second wavelength g-line is positive as compared to the reference image size shown in FIG. It can be seen that the Therefore, based on step 55, in step 56, the cemented lens LB1 to be replaced is replaced with a lens having a small curvature radius of the cemented surface SS.

  FIG. 8 shows measured values when the cemented lens LB1 is replaced with a cemented lens in which the radius of curvature of the cemented surface SS is 46.52 mm. As shown at the wide-angle end (FIG. 8A) and at the telephoto end (FIG. 8B), it can be seen that lateral chromatic aberration is corrected to a state close to the reference state.

  The cemented lens LB1 to be replaced is a lens that does not move during zooming in the zoom lens system 10, and even if it is replaced, the influence of the zooming performance is small. Furthermore, the cemented lens LB1 belongs to the second lens group G2 that moves along the optical axis during focusing, and is not the lens L16 at the end on the reduction side, nor the lens L1 at the end on the enlargement side. In the cemented lens LB1 meeting this condition, even if the chief ray passing through the cemented surface SS becomes almost parallel to the optical axis 7 and the radius of curvature of the cemented surface SS is changed, aberration correction other than correction of lateral chromatic aberration, For example, it hardly affects correction of curvature of field, astigmatism, and coma.

  In particular, even if the principal ray around the image, for example, the principal ray emitted from the end of the light modulation device 5 in the projector 1 of this example, is substantially parallel to the optical axis 7 in the vicinity of the junction surface SS. become. In the case of a zoom lens system for imaging, the chief ray incident on the end of the imaging device is substantially parallel to the optical axis 7 as it passes through the cemented surface. Almost parallel means that the angle that the chief ray makes with the optical axis 7 is relatively small, for example, 5 degrees or less, preferably 3 degrees or less.

  The difference between the radius of curvature of the cemented surface SS of the cemented lens LB1 to be replaced and the radius of curvature of the cemented surface SS before replacement is preferably within 3%, and more preferably within 1%. In the above example, the cemented lens is replaced by a cemented lens with a curvature radius difference of around 2%. For example, a cemented lens with a curvature radius difference of around 1% is prepared in advance up to about 3% and measured It can be replaced with a cemented lens of a radius of curvature suitable for correcting the lateral chromatic aberration.

  FIG. 9 shows an overview of a projector 1 including different lens systems 10. The lens system 10 is a zoom lens system 10 including sixteen lenses in a nine-group configuration including a first lens group G1 to a ninth lens group G9 arranged in order from the enlargement side 3. When zooming from the wide angle end (WIDE) shown in FIG. 9A to the telephoto end (TELE) in FIG. 9B, the fourth lens group G4 to the eighth lens group G8 move. On the other hand, the first lens group G1 to the third lens group G3 and the ninth lens group G9 do not move during zooming, and the second lens group G2 and the third lens group G3 do not move for focusing. Move when. Furthermore, the third lens group G3 includes a cemented lens LB1.

  Therefore, the third lens group G3 of the lens system 10 is a target lens group that does not move during zooming but moves along the optical axis 7 during focusing. In addition, the third lens group G3 does not include the lens at the end of the reduction side 2 and the lens at the end of the enlargement side 3 of the zoom lens system 10, and includes the cemented lens LB1. Therefore, in the zoom lens system 10, as the cemented lens (first cemented lens) to be replaced, the cemented lens LB1 can be replaced with a lens having a different curvature radius of the cemented surface SS to correct magnification chromatic aberration. It can be set (step 51).

  The configuration of the zoom lens system 10 will be described in more detail. The first lens group G1 on the most enlargement side 3 is a fixed lens group that has a positive refractive power as a whole and does not move during zooming, and does not move during focusing. The first lens group G1 includes a positive meniscus lens L1 convex on the enlargement side 3.

  The second lens group G2 is a fixed lens group that has a negative refractive power as a whole and does not move during zooming, and the reduction side 2 is used when moving the focus from a near distance to a far distance during focusing. Is a moving lens group that moves to the The second lens group G2 includes negative meniscus lenses L2 and L3 convex on the enlargement side.

  The third lens group G3 is a fixed lens group that has a negative refractive power as a whole and does not move during zooming. When focusing is performed, the reduction side 2 is used when moving the focus from a short distance to a long distance. Move to The third lens group G3 is a negative meniscus lens that is entirely convex on the reduction side 2 and includes a cemented doublet lens (first cemented lens) LB1. The cemented lens LB1 includes a biconcave negative lens L4 and a biconvex positive lens L5.

  The fourth lens group G4 has a positive refractive power as a whole, and is a moving lens group that moves during zooming, and does not move during focusing. The fourth lens group G4 includes a biconvex positive lens L6.

  The fifth lens group G5 is a moving lens group that has a negative refractive power as a whole and moves during zooming, and does not move during focusing. The fifth lens group G5 includes a biconcave negative lens L7.

  The sixth lens group G6 is a moving lens group that has a positive refractive power as a whole and moves with the stop St disposed on the reduction side 2 during zooming, and does not move during focusing. The sixth lens group G6 includes a biconvex positive lens L8.

  The seventh lens group G7 has a positive refractive power as a whole, and is a moving lens group that moves during zooming, and does not move during focusing. The seventh lens group G7 includes a double convex type cemented lens LB2. The doublet lens LB2 includes a double convex positive lens L9 and a negative meniscus lens L10 convex on the reduction side 2.

  The eighth lens group G8 is a moving lens group that has a positive refractive power as a whole, and moves during zooming, and does not move during focusing. The eighth lens group G8 includes, in order from the enlargement side 3, a cemented doublet lens LB3 of positive meniscus type convex to the reduction side 2 and two sheets of negative meniscus type convex to the reduction side 2 And a biconvex positive lens L15. The cemented lens LB3 includes a biconcave negative lens L11 and a biconvex positive lens L12. The cemented lens LB4 includes a negative meniscus lens L13 convex on the reduction side 2 and a positive meniscus lens L14 convex on the reduction side 2.

  The ninth lens group G9 on the most reduction side 2 is a fixed lens group that has a positive refractive power as a whole and does not move during zooming, and does not move during focusing. The ninth lens group G9 includes a positive meniscus lens L16 convex on the enlargement side 3.

  The numerical values of the zoom lens system 10 are shown in FIG. 10A shows lens data of the lens system 10, FIG. 10B shows zoom data of the lens system 10, and FIG. 10C shows aspheric surface data of the lens system 10. Both surfaces of the negative meniscus lens L2 of the second lens group G2 are aspheric.

  FIG. 11 shows the design value (reference value) of the magnification chromatic aberration of the zoom lens system 1. FIG. 11 (a) is a design value of magnification chromatic aberration at the wide angle end, and FIG. 11 (b) is a design value of magnification chromatic aberration at the telephoto end.

  FIG. 12 shows an example of lateral chromatic aberration measured in the lens system 10 in a state (reference state) assembled based on the lens data shown in FIG. 10 (step 52). FIG. 12A is an actual measurement value of lateral chromatic aberration at the wide-angle end, and FIG. 12B is an actual measurement value of lateral chromatic aberration at the telephoto end. The radius of curvature of the cemented surface SS of the cemented lens LB1 to be replaced in this figure is 26.993 mm of the reference radius.

  It can be seen that the measured image size of the second wavelength, the g-line, is shifted to the negative side at both the wide angle end and the telephoto end, as compared with the reference image size shown in FIG. Therefore, based on step 53, in step 54, the cemented lens LB1 to be replaced is replaced with a lens having a large radius of curvature of the cemented surface SS.

  FIG. 13 shows measured values when the cemented lens LB1 is replaced with a cemented lens in which the curvature radius of the cemented surface SS is 27.6 mm. As shown at the wide-angle end (FIG. 13A) and at the telephoto end (FIG. 13B), it can be seen that the lateral chromatic aberration is corrected to a state close to the reference state.

  FIG. 14 shows an example of lateral chromatic aberration measured in another lens system 10 in a state (reference state) assembled based on the lens data shown in FIG. 10 (step 52). At the wide-angle end (FIG. 14 (a)) and the telephoto end (FIG. 14 (b)), the measured image size of the second wavelength, g-line, is positive as compared to the reference image size shown in FIG. It can be seen that the Therefore, based on step 55, in step 56, the cemented lens LB1 to be replaced is replaced with a lens having a small curvature radius of the cemented surface SS.

  FIG. 15 shows measured values when the cemented lens LB1 is replaced with a cemented lens having a curvature radius of 26.4 mm on the cemented surface SS. As shown at the wide-angle end (FIG. 15 (a)) and at the telephoto end (FIG. 15 (b)), it can be seen that lateral chromatic aberration is corrected to a state close to the reference state.

  As described above, the zoom lens system 10 is a fixed lens that does not move during zooming, is moved during focusing, and is disposed at a position that is not the most enlargement 3 or the most reduction 2 When the cemented lens LB1 is provided, when the magnification chromatic aberration deviates from a predetermined value, the cemented lens LB1 is replaced with a cemented lens having a different curvature radius of the cemented surface as a lens to be replaced. The chromatic aberration can be brought close to a predetermined value. The manufacturing method shown above is applicable not only to the lens system for a projector but to the lens system for imaging. Further, the specific group configuration and lens configuration of the zoom lens system 10 are not limited to the above, and when the cemented lens defined above is included in the zoom lens system 10, the cemented lens is used as a replacement target, and the magnification Correction of chromatic aberration can be improved.

1 projector 10 zoom lens system LB1 first cemented lens

Claims (9)

A method of manufacturing a zoom lens system,
Obtaining the chromatic aberration of magnification of the zoom lens system of an entity;
The obtained magnification chromatic aberration comprises replacing at least one lens included in the designed zoom lens system,
In the replacement, there is an objective lens group which does not move during zooming but moves along the optical axis at the time of focusing, and the objective lens group is a lens at the end on the reduction side of the zoom lens system And the lens at the end on the enlargement side, if the target lens group includes the first cemented lens, the radius of curvature of the surface on the enlargement side and the curvature of the face on the reduction side Method including replacing with a cemented lens in which the radius is the same and the radius of curvature of the cemented surface is different. In claim 1,
What is obtained is: a second entity image size of a second wavelength whose wavelength is short with respect to the first wavelength, based on the entity image size of the first wavelength of the zoom lens system; Obtaining the third image size of the third wavelength with a long wavelength for one wavelength,
The above replacement is
A second reference image size of the second wavelength and a third reference image of the third wavelength based on the image size of the first wavelength calculated based on the specifications of the zoom lens system For size and
If the second entity image size is negative with respect to the second reference image size, or the third entity image size is plus with respect to the third reference image size, the first Replacing the cemented lens of the present invention with a cemented lens having a large radius of curvature of the cemented surface,
If the second entity image size is plus with respect to the second reference image size, or the third entity image size is minus with respect to the third reference image size, the first And V. replacing the cemented lens with a cemented lens having a small radius of curvature of the cemented surface. In claim 1 or 2,
The method of replacing includes replacing the first cemented lens with a cemented lens having a difference in curvature radius of cemented surface within 3%. In any one of claims 1 to 3,
The replacing includes replacing the first cemented lens with a cemented lens having a difference in curvature radius of cemented surface within 1%. In any one of claims 1 to 4,
Said obtaining comprises measuring the chromatic aberration of magnification of the zoom lens system of said entity. In any one of claims 1 to 4,
What is obtained is obtained by redesigning the design data of the zoom lens system of the entity, reflecting the glass material data obtained by actually measuring the actual glass material used for each lens of the zoom lens system of the entity. Analyzing by simulation based on the designed design data to measure lateral chromatic aberration. What is claimed is: 1. A zoom lens system having a target lens group that does not move during zooming but moves along an optical axis during focusing,
The target lens group does not include the lens at the reduction end and the lens at the enlargement end of the zoom lens system, and the curvature radius of the enlargement side surface due to the magnification chromatic aberration of the actual zoom lens system at the time of manufacture A zoom lens system, comprising: a first cemented lens to be replaced by a cemented lens in which the curvature radius of the reduction side surface is the same and the curvature radius of the cemented surface is different. A zoom lens system according to claim 7;
And a light modulation device disposed on the reduction side of the zoom lens system. A zoom lens system according to claim 7;
And an imaging device disposed on the reduction side of the zoom lens system.

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