WO2009088120A1 - Self-compensating apparatus of interference-fringe-generating position to compensate optical path difference result from objectives lens working distance variation for environment temperature variation in regard of interference lens - Google Patents
Self-compensating apparatus of interference-fringe-generating position to compensate optical path difference result from objectives lens working distance variation for environment temperature variation in regard of interference lens Download PDFInfo
- Publication number
- WO2009088120A1 WO2009088120A1 PCT/KR2008/001090 KR2008001090W WO2009088120A1 WO 2009088120 A1 WO2009088120 A1 WO 2009088120A1 KR 2008001090 W KR2008001090 W KR 2008001090W WO 2009088120 A1 WO2009088120 A1 WO 2009088120A1
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- WIPO (PCT)
- Prior art keywords
- objective lens
- interference
- variation
- fringe generating
- interference fringe
- Prior art date
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Classifications
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/24—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures
- G01B11/2441—Measuring arrangements characterised by the use of optical techniques for measuring contours or curvatures using interferometry
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B1/00—Measuring instruments characterised by the selection of material therefor
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B9/00—Measuring instruments characterised by the use of optical techniques
- G01B9/02—Interferometers
- G01B9/02055—Reduction or prevention of errors; Testing; Calibration
- G01B9/02062—Active error reduction, i.e. varying with time
- G01B9/02064—Active error reduction, i.e. varying with time by particular adjustment of coherence gate, i.e. adjusting position of zero path difference in low coherence interferometry
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B9/00—Measuring instruments characterised by the use of optical techniques
- G01B9/02—Interferometers
- G01B9/0209—Low-coherence interferometers
Definitions
- the present invention relates to an apparatus for self- compensating a position of an interference fringe generating part with respect to variation in a working distance of an objective lens according to environment temperature variation in an interference lens, and more particularly, to a self- compensating apparatus which varies proportionally a length of an interference fringe generating position adjusting part connected with an interference fringe generating part to minimize a difference between optical path from a half mirror in the interference fringe generating part to a reference mirror and the half mirror in the interference fringe generating part to the surface of the object to be measured in contradistinction with variation in a working distance of an objective lens according to environment temperature variation in an interference lens .
- optical measuring equipments are used to measure a three-dimensional shape on a surface of an object, and particularly, an interference lens is used to accurately measure the three-dimensional surface shape on the object surface.
- the interference lens includes an objective lens for obtaining an image of the surface of the object and an interference fringe generating part for generating an interference fringe pattern.
- the surface of the object is firstly adjusted to be placed at the working distance of the objective lens so that the image of the surface of the object can be clearly obtained, and next, a position of the interference fringe generating part is adjusted so that the interference fringe pattern is most clearly obtained (i. e. an amplitude of the interference fringe pattern is largest; the amplitude of the interference fringe pattern may be referred to as a "visibility" .
- an interference lens with high magnification is used to raise the accuracy of the three-dimensional shape measurement for the surface of the object to nanometer level
- interference lens with high magnification employs an objective lens with high magnification and thus sensitivity with respect to a relative position of the interference fringe generating part is largely- increased in contradistinction with a working distance of the objective lens since a depth of focus of the objective lens is very small due to its characteristic. That is to say, since the position of the interference fringe generating part, with respect to variation amount of the working distance of the objective lens due to variation in environment temperature, is hardly changed from the initially adjusted position, the image including the interference fringe pattern is not clear. Such damaged clearness of the image including the interference fringe pattern causes errors in the shape measurement and eventually be a cause of lowering the accuracy of the shape measurement for the surface of the object
- a light left from an objective lens 10 is split into two ways at a half mirror 33a of an interference fringe generating part 33.
- One light reflected from the half mirror 33a is transmitted to a reference mirror 33b and the other light passing through the half mirror 33a is transmitted to an object 1 to be measured.
- the lights respectively arrived at the reference mirror 33b and the object 1 are reflected or scattered on surface of the reference mirror 33b and surface of the object 1 and then joined again at the half mirror 33a.
- the joined light is then transmitted to the objective lens 10, thereby forming an image of the surface of the object 1 and the reference mirror 33b.
- the lights respectively reflected from the reference mirror 33b and the surface of the object 1 are joined at the half mirror 33a, if the lights respectively reflected from the reference mirror 33b and the of the object 1 have the same optical paths, the lights interfere with each other to form an interference fringe pattern with respect to the shape of the surface of the object.
- the interference is generated only when the optical path from the half mirror 33a to the reference mirror 33b and the optical path from the half mirror 33a to the surface of the object 1 are the same.
- FIG. 1 (a) of Fig 1 is a cross sectional view illustrating the case that the working distance of the objective lens 10 and the relative position of the interference fringe generating part 33 are well matched at some temperature, in which the optical path from the half mirror 33a to the surface of the object 1 and the optical path from the half mirror 33a to the reference mirror 33b accord well.
- FIG. 1 is a cross sectional view illustrating the case that the working distance " ⁇ " of the objective lens 10 is varied by variation amount " ⁇ ” and the length " ⁇ " of the interference fringe generating position adjusting part 30 is varied by variation amount " ⁇ ” as environment temperature is increased and thus the whole interference lens 50 or the object 1 is moved to accord surface of the object 1 with the position of varied working distance " ⁇ + ⁇ ” of the objective lens 10 so as to obtain a clear image, in which a difference " ⁇ - ⁇ " between the optical path from the half mirror 33a to the surface of the object 1 and the optical path from the half mirror 33a to the reference mirror 33b is generated.
- FIG. 1 is a cross sectional view illustrating the case that the interference fringe generating position adjusting part 30 is manually adjusted by the optical path difference " ⁇ - ⁇ " from the state of (b) of Fig. 1 so that the optical path from the half mirror 33a to the surface of the object 1 and the optical path from the half mirror 33a to the reference mirror 33b become identical, in which the adjustment is made so that the image of the surface of the object 1 including the interference fringe pattern can be clearly obtained as is (a) of Fig. 1.
- the working distance " ⁇ " of the objective lens 10 is varied by “ ⁇ ” as the environment temperature is varied and the relative position of the interference fringe generating part 33 is also varied as the length of " ⁇ " of the interference fringe generating position adjusting part 30 is varied by “ ⁇ ” according to thermal expansion or thermal contraction. Therefore, the distance from the half mirror 33a of the interference fringe generating part 33 to the surface of the object 1 and the optical path from the half mirror 33a to the reference mirror 33b are varied by " ⁇ - ⁇ ".
- the optical path difference " ⁇ - ⁇ ” can be eliminated and consequently measuring error can be reduced only when the position of the interference fringe generating part 33 is adjusted by rotationally raising or lowering the interference fringe generating position adjusting part 30 by " ⁇ - ⁇ " as shown in (c) of Fig. 1 for compensating such optical path difference " ⁇ - ⁇ ". Therefore, the interference lens 50 has a problem that the optical path difference " ⁇ - ⁇ " due to the temperature variation should be frequently compensated.
- Such manual compensating process has problems that the measurement cannot be quickly performed since the manual compensating process is very complicated and thus takes much time, and, in addition, it is difficult to ensure the accuracy of the measurement since a minute difference in compensating level is necessarily generated according to proficiencies of workers. Further, since such manual compensating process is performed by hand, it is difficult to develop toward automated (unmanned) measuring equipment. Furthermore, there is a problem that frequent adjustment of the interference fringe generating position adjusting part 30 causes abrasion of screws in the interference fringe generating position adjusting part 30 and consequently reduces the lifespan of the interference lens 50.
- An object of the present invention is to provide a self- compensating apparatus for minimizing a difference between a optical paths from a half mirror in an interference fringe generating part to a surface of the object to be measured and a optical path from the half mirror to a reference mirror which is generated due to variation in working distance of an objective lens according to temperature variation in an interference lens .
- another object of the present invention is to provide an apparatus which eliminates a clearance generated due to space between threads according to screw fastening of an interference generating position adjusting part and thus prevents generation of a difference between the optical paths due to the clearance itself.
- the self-compensating apparatus of an inference fringe generating position for compensating a optical path difference generated due to variation in working distance of an objective lens according to environment temperature variation in an interference lens includes an objective lens (10) which is capable of adjusting a distance from an object (1) to be measured and forms an image of the surface of the object (1) ; an adapter (20) which receives a barrel (11) of the objective lens (10) and fastened to the outside surface of the objective lens 10 so as to be capable of moving up and down in response to the variation in the length of the barrel (11) ; an interference fringe generating part (33) which is placed at the opposite side to the objective lens (10) and generates an interference fringe pattern the image of the surface of the object (1) ; and an interference fringe generating position adjusting part (30) which receives the adapter (20) and varies a position of the interference fringe generating part (33) in response to the length variation of the barrel of the objective lens 10. Also, an air ventilation gap having a predetermined space is formed between the adapter (20) and the barrel (11) of the
- the interference fringe generating position adjusting part (30) includes a mounting part (32) which receives the lower outer side of the adapter (20) in the longitudinal direction and secures the interference fringe generating part (33) .
- interference fringe generating position adjusting part (30) further include a mounting reference part
- the interference fringe generating position adjusting part (30) varies the position of the interference fringe generating part (33) by the mounting part (32) and the mounting reference part (31) of which lengths are respectively varied in correspondence to the variation amount of the length of the barrel (11) of the objective lens (10) according to the temperature variation.
- the mounting part (32) and the mounting reference part (31) are fastened by a screw fastening.
- the mounting part (32) and the mounting reference part (31) are formed integrally with each other. Further, a material of the adapter (20) is invar or super invar having small length variation according to the temperature variation.
- an elastic means (34) is inserted between and elastically supports the mounting reference part (31) and the mounting part (32) so as to prevent a clearance due to the screw fastening of the mounting reference part (31) and the mounting part (32) .
- a material of the adapter (20) is invar or super invar having small length variation according to the temperature variation.
- an elastic means (34) is inserted between and elastically supports the mounting reference part (31) and the mounting part (32) so as to prevent a clearance due to the screw fastening of the mounting reference part (31) and the mounting part (32) .
- the elastic means (34) is a spring.
- the adapter (20) and the interference fringe generating position adjusting part (30) are respectively formed with a screw thread (21) and a screw fastening thread (35) and fastened by the screw thread (21) and the screw fastening thread (35) , and a coupling screw (40) coupled at the outside of the interference fringe generating position adjusting part (30) , and a pressurization part (41) , which has a lower strength than the screw thread (21) of the adapter (20) , is provided in the inside of the coupling screw (40) and is pressurized to the screw thread (21) of the adapter (20) and plastically deformed by the fastening of the coupling screw (40) , are further provided so as to prevent a clearance due to the screw fastening of the screw thread (21) and the screw fastening thread (35) .
- the self-compensating method of an inference fringe generating position for compensating a optical path difference generated due to variation in working distance of an objective lens according to environment temperature variation in an interference lens includes adjusting a distance between an objective lens (10) and surface of the object (1) to be measured so as to form an image of the surface of the object (1) on the objective lens (10) ; adjusting a position of an interference fringe pattern generated by an interference fringe generating part (33) by adjusting a position of the interference fringe generating position adjusting part (30) after the adjustment of the distance between the objective lens (10) and the surface of the object (1) ; and automatically adjusting a position of the image of the surface of the object
- Fig. 1 is a cross-sectional view illustrating a conventional interference lens .
- Fig. 2 is a view for explaining an apparatus for self- compensating a position of an interference fringe generating part with respect to variation in working distance of an objective lens according to environment temperature variation in an interference lens in accordance with the present invention.
- Fig. 3 is a cross-sectional view illustrating an apparatus for self-compensating a position of an interference fringe generating part with respect to variation in working distance of an objective lens according to environment temperature variation in an interference lens in accordance with an embodiment of the present invention.
- Fig. 4 is a cross-sectional view illustrating an apparatus for self -compensating a position of an interference fringe generating part with respect to variation in working distance of an objective lens according to environment temperature variation in an interference lens in accordance with another embodiment of the present invention.
- the present invention relates to an apparatus for self- compensating a position of an interference fringe generating part 33 so as to compensate a optical path difference generated due to variation in working distance of objective lens 10 according to environment temperature variation in an interference lens 50.
- Fig. 2 is a view for explaining the apparatus for self- compensating the position of the interference fringe generating part 33 so as to minimize a optical path difference due to environment temperature variation of the interference lens 50 in accordance with the present invention.
- ⁇ is a working distance of the objective lens 10 before the temperature variation
- ⁇ is a length of the interference fringe generating position adjusting part 30 before the temperature variation
- ⁇ is a length of a barrel 11 of the objective lens 10 before the temperature variation.
- ⁇ is the variation amount of the working distance of the objective lens 10 after the temperature variation
- ⁇ is the variation amount of the length of a barrel 11 of the objective lens 10 after the temperature variation
- ⁇ is the variation amount of the length of the interference fringe generating position adjusting part 30 after the temperature variation.
- a lower inner surface of an adapter 20 is fixed to a lower outer surface of the objective lens 10 and an upper inner surface of the interference fringe generating position adjusting part 30 is fixed to an upper outer surface of the adapter 20.
- the interference fringe generating part 33 is fixed to a lower part of the interference fringe generating position adjusting part 30.
- the material for the interference fringe generating position adjusting part 30 In order to move the whole interference fringe generating position adjusting part 30 by the same distance as the " ⁇ y" is the variation amount of the length of the barrel 11 of the objective lens 10 in the variation direction of the length of the barrel 11 of the objective lens 10 according to the temperature variation, it is preferable to use a material which has almost no thermal expansion (for example, a material such as invar, super invar, etc.) as a material for adapter 20, and a material, which has a thermal expansion coefficient capable of compensate the variation amount " ⁇ " of the working distance of the objective lens 10 according to the temperature variation, is used as the material for the interference fringe generating position adjusting part 30.
- a material which has almost no thermal expansion for example, a material such as invar, super invar, etc.
- Fig. 3 is a cross-sectional view illustrating an embodiment of the present invention
- Fig. 4 is a cross- sectional view illustrating another embodiment of the present invention.
- the objective lens 10 within the interference lens 50 is a component which is known to be capable of adjusting a distance from the surface of the object 1 and to serve to form the image of the surface of the object 1.
- the adapter 20 receives the barrel 11 of the objective lens 10 and is fastened to the lower outer surface of the objective lens 10 so as to be capable of that moving up and down according to the variation in the length of the barrel 11 of the objective lens 10 due to the temperature variation.
- the interference fringe generating position adjusting part 30 receives the adapter 20 and fixed to the upper outer side of the adapter 20.
- the interference fringe generating position adjusting part 30 includes a mounting reference part 31 formed with a screw thread 31a at the lower outer side thereof and a mounting part 32 provided with a screw fastening thread 32a which is fastened to the screw thread 31a of the mounting reference part 31 and fixes the interference fringe generating part 33 to the lower end part thereof, the interference fringe generating part 33 being located at the lower part of the objective lens 10 and generating the interference fringe pattern.
- the adapter 20 When the environment temperature is increased, the barrel 11 of the objective lens 10 is lengthened and thus the adapter 20 is moved down. Also, the adapter 20 is lengthened with the increase of the environment temperature, and this moves up the interference fringe generating position adjusting part 30 which is fixed to the adapter 20. The interference fringe generating position adjusting part 30 is moved up by the adapter 20 but the interference fringe generating position adjusting part 30 is also lengthened with the increase in the environment temperature. Therefore, the interference fringe generating part 33 is moved down. At this time, with an adjustment of the moving-down length of the interference fringe generating part 33 in the direction in which the barrel 11 of the objective lens 10 is lengthened, it is possible to compensate the optical path difference generated due to the variation in the working distance of the objective lens 10 according to the temperature variation.
- the optical path difference is compensated in such a manner that the position of the interference fringe generating part 33 due to the difference between the variation amount of the length of the mounting reference part 31 and the mounting part 32 according to the temperature variation and the variation amount of the length of the adapter 20 according to the temperature variation is varied correspondingly to the variation amount of the length of the barrel 11 of the objective lens 10 according to the temperature variation.
- a gap 22 for air ventilation with a predetermined space through which air can be ventilated is formed between the adapter 20 and the barrel 11 of the objective lens 10. Since the barrel 11 of the objective lens 10 is smoothly in contact with the air by the gap 22, the length of the barrel 11 of the objective lens 10 can be smoothly varied according to the temperature variation.
- invar or super invar having small length variation according to the temperature variation is used as the material of the adapter 20 and thus the adapter 20 has almost no length variation according to the temperature variation, and the variation amount of the working distance of the objective lens 10 itself according to the temperature variation can be compensated by adding the variation amount of the length of the barrel 11 of the objective lens 10 according to the temperature variation and the variation amount of the length of the mounting reference part 31 and the mounting part 32 according to the temperature variation.
- the mounting reference part 31 and the mounting part 32 are fastened by screw fastening and it is also preferable that, in order to prevent a clearance due to the screw fastening, an elastic means 34 is inserted between the mounting reference part 31 and the mounting part 32 to elastically support the mounting reference part 31 and the mounting part 32 with respect to each other. At this time, it is more preferable that the elastic means 34 is a spring.
- the interference fringe generating position adjusting part 30 may be formed in the separate mounting reference part 31 and mounting part 32 as shown in Fig. 3, but may be formed integrally into a single body as shown in Fig. 4, Also, it is preferable that, as shown in Fig.
- the adapter 20 and the interference fringe generating position adjusting part 30 are respectively formed with a screw thread 21 and a screw fastening thread 35 and fastened by the screw thread 21 and the screw fastening thread 35, and a coupling screw 40 coupled at the outside of the interference fringe generating position adjusting part 30 and a pressurization part 41, which has a lower strength than the screw thread 21 of the adapter 20 and is provided in the inside of the coupling screw 40 and is pressurized to the screw thread 21 of the adapter 20 and plastically deformed by the fastening of the coupling screw 40, are further provided so as to prevent a clearance due to the screw fastening of the screw thread 21 and the screw fastening thread 35.
- resin material is used for the pressurization part 41.
- the variation amount of the length of the interference fringe generating position adjusting part 30 according to the temperature variation can be constant .
Abstract
The present invention relates to an apparatus for self-compensating a position of an interference fringe generating part to compensate a optical path difference, and includes an objective lens which forms an image of the surface of the object; an adapter which receives a barrel of the objective lens and fastened to the outside surface of the objective lens; an interference fringe generating part which is placed at the opposite side to the objective lens and generates an interference fringe pattern the image of the surface of the object; and an interference fringe generating position adjusting part which receives the adapter and varies a position of the interference fringe generating part in response to the length variation of the barrel of the objective lens.
Description
[DESCRIPTION] [invention Title]
SELF-COMPENSATING APPARATUS OF INTERFERENCE-FRINGE-
GENERATING POSITION TO COMPENSATE OPTICAL PATH DIFFERENCE RESULT FROM OBJECTIVES LENS WORKING DISTANCE VARIATION FOR
ENVIRONMENT TEMPERATURE VARIATION IN REGARD OF INTERFERENCE
LENS
[Technical Field] The present invention relates to an apparatus for self- compensating a position of an interference fringe generating part with respect to variation in a working distance of an objective lens according to environment temperature variation in an interference lens, and more particularly, to a self- compensating apparatus which varies proportionally a length of an interference fringe generating position adjusting part connected with an interference fringe generating part to minimize a difference between optical path from a half mirror in the interference fringe generating part to a reference mirror and the half mirror in the interference fringe generating part to the surface of the object to be measured in contradistinction with variation in a working distance of an objective lens according to environment temperature variation in an interference lens .
[Background Art]
Generally, in industrial fields, optical measuring equipments are used to measure a three-dimensional shape on a surface of an object, and particularly, an interference lens is used to accurately measure the three-dimensional surface shape on the object surface.
The interference lens includes an objective lens for obtaining an image of the surface of the object and an interference fringe generating part for generating an interference fringe pattern. In order to measure the surface shape, the surface of the object is firstly adjusted to be placed at the working distance of the objective lens so that the image of the surface of the object can be clearly obtained, and next, a position of the interference fringe generating part is adjusted so that the interference fringe pattern is most clearly obtained (i. e. an amplitude of the interference fringe pattern is largest; the amplitude of the interference fringe pattern may be referred to as a "visibility") .
In recent, an interference lens with high magnification is used to raise the accuracy of the three-dimensional shape measurement for the surface of the object to nanometer level
(lnm=0.000001mm) . However, such interference lens with high magnification employs an objective lens with high magnification and thus sensitivity with respect to a relative
position of the interference fringe generating part is largely- increased in contradistinction with a working distance of the objective lens since a depth of focus of the objective lens is very small due to its characteristic. That is to say, since the position of the interference fringe generating part, with respect to variation amount of the working distance of the objective lens due to variation in environment temperature, is hardly changed from the initially adjusted position, the image including the interference fringe pattern is not clear. Such damaged clearness of the image including the interference fringe pattern causes errors in the shape measurement and eventually be a cause of lowering the accuracy of the shape measurement for the surface of the object
This will be described with reference to a conventional interference lens 50 as follows.
As shown in (a) of Fig. 1, a light left from an objective lens 10 is split into two ways at a half mirror 33a of an interference fringe generating part 33. One light reflected from the half mirror 33a is transmitted to a reference mirror 33b and the other light passing through the half mirror 33a is transmitted to an object 1 to be measured. The lights respectively arrived at the reference mirror 33b and the object 1 are reflected or scattered on surface of the reference mirror 33b and surface of the object 1 and then
joined again at the half mirror 33a. The joined light is then transmitted to the objective lens 10, thereby forming an image of the surface of the object 1 and the reference mirror 33b.
During this process, when the lights respectively reflected from the reference mirror 33b and the surface of the object 1 are joined at the half mirror 33a, if the lights respectively reflected from the reference mirror 33b and the of the object 1 have the same optical paths, the lights interfere with each other to form an interference fringe pattern with respect to the shape of the surface of the object. In other words, the interference is generated only when the optical path from the half mirror 33a to the reference mirror 33b and the optical path from the half mirror 33a to the surface of the object 1 are the same. (a) of Fig 1 is a cross sectional view illustrating the case that the working distance of the objective lens 10 and the relative position of the interference fringe generating part 33 are well matched at some temperature, in which the optical path from the half mirror 33a to the surface of the object 1 and the optical path from the half mirror 33a to the reference mirror 33b accord well.
(b) of Fig. 1 is a cross sectional view illustrating the case that the working distance "α" of the objective lens 10 is varied by variation amount "Δα" and the length "β" of the
interference fringe generating position adjusting part 30 is varied by variation amount "Δβ" as environment temperature is increased and thus the whole interference lens 50 or the object 1 is moved to accord surface of the object 1 with the position of varied working distance "α+ Δα" of the objective lens 10 so as to obtain a clear image, in which a difference "Δα-Δβ" between the optical path from the half mirror 33a to the surface of the object 1 and the optical path from the half mirror 33a to the reference mirror 33b is generated. (c) of Fig. 1 is a cross sectional view illustrating the case that the interference fringe generating position adjusting part 30 is manually adjusted by the optical path difference "Δα- Δβ" from the state of (b) of Fig. 1 so that the optical path from the half mirror 33a to the surface of the object 1 and the optical path from the half mirror 33a to the reference mirror 33b become identical, in which the adjustment is made so that the image of the surface of the object 1 including the interference fringe pattern can be clearly obtained as is (a) of Fig. 1. In other words, in the interference lens 50, the working distance "α" of the objective lens 10 is varied by "Δα" as the environment temperature is varied and the relative position of the interference fringe generating part 33 is also varied as the length of "β" of the interference fringe generating
position adjusting part 30 is varied by "Δβ" according to thermal expansion or thermal contraction. Therefore, the distance from the half mirror 33a of the interference fringe generating part 33 to the surface of the object 1 and the optical path from the half mirror 33a to the reference mirror 33b are varied by "Δα-Δβ".
The optical path difference "Δα-Δβ" can be eliminated and consequently measuring error can be reduced only when the position of the interference fringe generating part 33 is adjusted by rotationally raising or lowering the interference fringe generating position adjusting part 30 by "Δα-Δβ" as shown in (c) of Fig. 1 for compensating such optical path difference "Δα-Δβ". Therefore, the interference lens 50 has a problem that the optical path difference "Δα-Δβ" due to the temperature variation should be frequently compensated.
Such manual compensating process has problems that the measurement cannot be quickly performed since the manual compensating process is very complicated and thus takes much time, and, in addition, it is difficult to ensure the accuracy of the measurement since a minute difference in compensating level is necessarily generated according to proficiencies of workers. Further, since such manual compensating process is performed by hand, it is difficult to develop toward automated (unmanned) measuring equipment. Furthermore, there is a
problem that frequent adjustment of the interference fringe generating position adjusting part 30 causes abrasion of screws in the interference fringe generating position adjusting part 30 and consequently reduces the lifespan of the interference lens 50.
[Disclosure] [Technical Problem]
An object of the present invention is to provide a self- compensating apparatus for minimizing a difference between a optical paths from a half mirror in an interference fringe generating part to a surface of the object to be measured and a optical path from the half mirror to a reference mirror which is generated due to variation in working distance of an objective lens according to temperature variation in an interference lens .
Also, another object of the present invention is to provide an apparatus which eliminates a clearance generated due to space between threads according to screw fastening of an interference generating position adjusting part and thus prevents generation of a difference between the optical paths due to the clearance itself.
[Technical Solution]
The self-compensating apparatus of an inference fringe generating position for compensating a optical path difference generated due to variation in working distance of an objective lens according to environment temperature variation in an interference lens includes an objective lens (10) which is capable of adjusting a distance from an object (1) to be measured and forms an image of the surface of the object (1) ; an adapter (20) which receives a barrel (11) of the objective lens (10) and fastened to the outside surface of the objective lens 10 so as to be capable of moving up and down in response to the variation in the length of the barrel (11) ; an interference fringe generating part (33) which is placed at the opposite side to the objective lens (10) and generates an interference fringe pattern the image of the surface of the object (1) ; and an interference fringe generating position adjusting part (30) which receives the adapter (20) and varies a position of the interference fringe generating part (33) in response to the length variation of the barrel of the objective lens 10. Also, an air ventilation gap having a predetermined space is formed between the adapter (20) and the barrel (11) of the objective lens (10) .
Also, the interference fringe generating position adjusting part (30) includes a mounting part (32) which
receives the lower outer side of the adapter (20) in the longitudinal direction and secures the interference fringe generating part (33) .
Further, the interference fringe generating position adjusting part (30) further include a mounting reference part
(31) which securely receives the upper outer side of the adapter (20) in the longitudinal direction and is coupled with the mounting part (32) .
Also, the interference fringe generating position adjusting part (30) varies the position of the interference fringe generating part (33) by the mounting part (32) and the mounting reference part (31) of which lengths are respectively varied in correspondence to the variation amount of the length of the barrel (11) of the objective lens (10) according to the temperature variation.
Also, the mounting part (32) and the mounting reference part (31) are fastened by a screw fastening.
Also, the mounting part (32) and the mounting reference part (31) are formed integrally with each other. Further, a material of the adapter (20) is invar or super invar having small length variation according to the temperature variation.
Also, in the interference fringe generating position adjusting part (30) , an elastic means (34) is inserted between
and elastically supports the mounting reference part (31) and the mounting part (32) so as to prevent a clearance due to the screw fastening of the mounting reference part (31) and the mounting part (32) . Further, a material of the adapter (20) is invar or super invar having small length variation according to the temperature variation.
Furthermore, the interference fringe generating position adjusting part (30) , an elastic means (34) is inserted between and elastically supports the mounting reference part (31) and the mounting part (32) so as to prevent a clearance due to the screw fastening of the mounting reference part (31) and the mounting part (32) .
Furthermore, the elastic means (34) is a spring. In addition, the adapter (20) and the interference fringe generating position adjusting part (30) are respectively formed with a screw thread (21) and a screw fastening thread (35) and fastened by the screw thread (21) and the screw fastening thread (35) , and a coupling screw (40) coupled at the outside of the interference fringe generating position adjusting part (30) , and a pressurization part (41) , which has a lower strength than the screw thread (21) of the adapter (20) , is provided in the inside of the coupling screw (40) and is pressurized to the screw thread (21) of the adapter (20)
and plastically deformed by the fastening of the coupling screw (40) , are further provided so as to prevent a clearance due to the screw fastening of the screw thread (21) and the screw fastening thread (35) . Also, the self-compensating method of an inference fringe generating position for compensating a optical path difference generated due to variation in working distance of an objective lens according to environment temperature variation in an interference lens includes adjusting a distance between an objective lens (10) and surface of the object (1) to be measured so as to form an image of the surface of the object (1) on the objective lens (10) ; adjusting a position of an interference fringe pattern generated by an interference fringe generating part (33) by adjusting a position of the interference fringe generating position adjusting part (30) after the adjustment of the distance between the objective lens (10) and the surface of the object (1) ; and automatically adjusting a position of the image of the surface of the object
(I) and the position of the interference fringe pattern by varying the position of the interference fringe generating part (33) in response to variation in the length of the barrel
(II) of the objective lens (10) according to environment temperature variation.
[Description of Drawings]
The above and other objects, features and advantages of the present invention will become apparent from the following description of preferred embodiments given in conjunction with the accompanying drawings, in which:
Fig. 1 is a cross-sectional view illustrating a conventional interference lens .
Fig. 2 is a view for explaining an apparatus for self- compensating a position of an interference fringe generating part with respect to variation in working distance of an objective lens according to environment temperature variation in an interference lens in accordance with the present invention.
Fig. 3 is a cross-sectional view illustrating an apparatus for self-compensating a position of an interference fringe generating part with respect to variation in working distance of an objective lens according to environment temperature variation in an interference lens in accordance with an embodiment of the present invention. Fig. 4 is a cross-sectional view illustrating an apparatus for self -compensating a position of an interference fringe generating part with respect to variation in working distance of an objective lens according to environment temperature variation in an interference lens in accordance
with another embodiment of the present invention.
[Detailed Description of Main Elements]
1: object to be measured
10: objective lens 11: barrel
20: adapter
30: interference fringe generating position adjusting part
31: mounting reference part 31a: screw part
33: interference fringe generating part
33a: half mirror
33b: reference mirror
34 : elastic means 50: interference lens
[Best Mode]
Hereinafter, the embodiments of the present invention will be described in detail with reference to accompanying drawings .
The present invention relates to an apparatus for self- compensating a position of an interference fringe generating part 33 so as to compensate a optical path difference generated due to variation in working distance of objective
lens 10 according to environment temperature variation in an interference lens 50.
To this end, as shown in Fig. 2, a concept of the present invention is to make a variation amount "Δα" in the working distance "α" of the objective lens according to the temperature variation and a variation amount "Δβ" of a length "β" of an interference fringe generating position adjusting part 30, to which the interference fringe generating part 33 including a half mirror 33a and a reference mirror 33b is connected, to be equal, i.e. "Δα = Δβ".
Fig. 2 is a view for explaining the apparatus for self- compensating the position of the interference fringe generating part 33 so as to minimize a optical path difference due to environment temperature variation of the interference lens 50 in accordance with the present invention.
Herein, "α" is a working distance of the objective lens 10 before the temperature variation; "β" is a length of the interference fringe generating position adjusting part 30 before the temperature variation; and "γ" is a length of a barrel 11 of the objective lens 10 before the temperature variation. Also, "Δα" is the variation amount of the working distance of the objective lens 10 after the temperature variation; "Δγ" is the variation amount of the length of a barrel 11 of the objective lens 10 after the temperature
variation; and "Δβ" is the variation amount of the length of the interference fringe generating position adjusting part 30 after the temperature variation.
In mechanical fixing between components, a lower inner surface of an adapter 20 is fixed to a lower outer surface of the objective lens 10 and an upper inner surface of the interference fringe generating position adjusting part 30 is fixed to an upper outer surface of the adapter 20. Also, the interference fringe generating part 33 is fixed to a lower part of the interference fringe generating position adjusting part 30. These are for proceeding of the length variations of respective components in opposite directions to each other when the temperature variation.
In order to move the whole interference fringe generating position adjusting part 30 by the same distance as the "Δy" is the variation amount of the length of the barrel 11 of the objective lens 10 in the variation direction of the length of the barrel 11 of the objective lens 10 according to the temperature variation, it is preferable to use a material which has almost no thermal expansion (for example, a material such as invar, super invar, etc.) as a material for adapter 20, and a material, which has a thermal expansion coefficient capable of compensate the variation amount "Δα" of the working distance of the objective lens 10 according to the temperature
variation, is used as the material for the interference fringe generating position adjusting part 30.
In other words, if the interference fringe generating position adjusting part 30 of the interference lens 50 is mechanically constructed as described above and the material of the components thereof is suitably selected in consideration of variation rate of the working distance of the objective lens 10 according to the temperature variation, it is possible to maintain the optical path from the half mirror 33a of the interference fringe generating part 33 to the surface of the object 1 and the optical path from the half mirror 33a to the reference mirror 33b to be accord with each other even though the working distance of the objective lens 10 is varied as the environment temperature is varied. Fig. 3 is a cross-sectional view illustrating an embodiment of the present invention and Fig. 4 is a cross- sectional view illustrating another embodiment of the present invention.
The objective lens 10 within the interference lens 50 is a component which is known to be capable of adjusting a distance from the surface of the object 1 and to serve to form the image of the surface of the object 1.
In Fig. 3, the adapter 20 receives the barrel 11 of the objective lens 10 and is fastened to the lower outer surface
of the objective lens 10 so as to be capable of that moving up and down according to the variation in the length of the barrel 11 of the objective lens 10 due to the temperature variation. The interference fringe generating position adjusting part 30 receives the adapter 20 and fixed to the upper outer side of the adapter 20. The interference fringe generating position adjusting part 30 includes a mounting reference part 31 formed with a screw thread 31a at the lower outer side thereof and a mounting part 32 provided with a screw fastening thread 32a which is fastened to the screw thread 31a of the mounting reference part 31 and fixes the interference fringe generating part 33 to the lower end part thereof, the interference fringe generating part 33 being located at the lower part of the objective lens 10 and generating the interference fringe pattern.
When the environment temperature is increased, the barrel 11 of the objective lens 10 is lengthened and thus the adapter 20 is moved down. Also, the adapter 20 is lengthened with the increase of the environment temperature, and this moves up the interference fringe generating position adjusting part 30 which is fixed to the adapter 20. The interference fringe generating position adjusting part 30 is moved up by the adapter 20 but the interference fringe generating position adjusting part 30 is also lengthened with the increase in the
environment temperature. Therefore, the interference fringe generating part 33 is moved down. At this time, with an adjustment of the moving-down length of the interference fringe generating part 33 in the direction in which the barrel 11 of the objective lens 10 is lengthened, it is possible to compensate the optical path difference generated due to the variation in the working distance of the objective lens 10 according to the temperature variation. In other words, the optical path difference is compensated in such a manner that the position of the interference fringe generating part 33 due to the difference between the variation amount of the length of the mounting reference part 31 and the mounting part 32 according to the temperature variation and the variation amount of the length of the adapter 20 according to the temperature variation is varied correspondingly to the variation amount of the length of the barrel 11 of the objective lens 10 according to the temperature variation.
Also, it is preferable that a gap 22 for air ventilation with a predetermined space through which air can be ventilated is formed between the adapter 20 and the barrel 11 of the objective lens 10. Since the barrel 11 of the objective lens 10 is smoothly in contact with the air by the gap 22, the length of the barrel 11 of the objective lens 10 can be smoothly varied according to the temperature variation.
At this time, it is preferable that invar or super invar having small length variation according to the temperature variation is used as the material of the adapter 20 and thus the adapter 20 has almost no length variation according to the temperature variation, and the variation amount of the working distance of the objective lens 10 itself according to the temperature variation can be compensated by adding the variation amount of the length of the barrel 11 of the objective lens 10 according to the temperature variation and the variation amount of the length of the mounting reference part 31 and the mounting part 32 according to the temperature variation.
Further, it is preferable that the mounting reference part 31 and the mounting part 32 are fastened by screw fastening and it is also preferable that, in order to prevent a clearance due to the screw fastening, an elastic means 34 is inserted between the mounting reference part 31 and the mounting part 32 to elastically support the mounting reference part 31 and the mounting part 32 with respect to each other. At this time, it is more preferable that the elastic means 34 is a spring. Accordingly, since sum of the lengths of the mounting reference part 31 and the mounting part 32 is always constant as the clearance due to the screw fastening is prevented, sum of respective variation amounts of the lengths
of the mounting reference part 31 and the mounting part 32 according to the temperature variation can be the same as the variation amount of the length when the mounting reference part 31 and the mounting part 32 are a single body. Furthermore, the interference fringe generating position adjusting part 30 may be formed in the separate mounting reference part 31 and mounting part 32 as shown in Fig. 3, but may be formed integrally into a single body as shown in Fig. 4, Also, it is preferable that, as shown in Fig. 4, the adapter 20 and the interference fringe generating position adjusting part 30 are respectively formed with a screw thread 21 and a screw fastening thread 35 and fastened by the screw thread 21 and the screw fastening thread 35, and a coupling screw 40 coupled at the outside of the interference fringe generating position adjusting part 30 and a pressurization part 41, which has a lower strength than the screw thread 21 of the adapter 20 and is provided in the inside of the coupling screw 40 and is pressurized to the screw thread 21 of the adapter 20 and plastically deformed by the fastening of the coupling screw 40, are further provided so as to prevent a clearance due to the screw fastening of the screw thread 21 and the screw fastening thread 35. At this time, resin material is used for the pressurization part 41. Accordingly, since the clearance due to the screw fastening of the screw
thread 21 and the screw fastening thread 35 is prevented when the pressurization part 41 is pressurized to the screw thread 21 of the adapter 20 and plastically deformed by the fastening of the coupling screw 40, it is the variation amount of the length of the interference fringe generating position adjusting part 30 according to the temperature variation can be constant .
[industrial Applicability] According to the present invention, by self-compensating the position of the interference generating part with respect to the optical path difference generated due to the variation in the working distance of the objective lens according to the temperature variation, it is possible to maintain clearness of the interference fringe pattern with respect to the image of the surface of the object to be measured as well as enhance the measuring accuracy. Further, since frequent manual adjustment is unnecessary, a measuring time is reduced and thus productivity is largely increased.
Claims
[CLAIMS]
[Claim l]
A self -compensating apparatus of an inference fringe generating position for compensating a optical path difference generated due to variation in working distance of an objective lens according to environment temperature variation in an interference lens, comprising: an objective lens (10) which is capable of adjusting a distance from an object (1) to be measured and forms an image of the surface of the object (1) ; an adapter (20) which receives a barrel (11) of the objective lens (10) and fastened to the outside surface of the objective lens 10 so as to be capable of moving up and down in response to the variation in the length of the barrel (11) ; an interference fringe generating part (33) which is placed at the opposite side to the objective lens (10) and generates an interference fringe pattern the image of the surface of the object (1) ; and an interference fringe generating position adjusting part (30) which receives the adapter (20) and varies a position of the interference fringe generating part (33) in response to the length variation of the barrel of the objective lens 10.
[Claim 2]
The self-compensating apparatus of an inference fringe generating position for compensating a optical path difference generated due to variation in working distance of an objective lens according to environment temperature variation in an interference lens as set forth in claim 1, wherein an air ventilation gap having a predetermined space is formed between the adapter 20 and the barrel 11 of the objective lens 10.
[Claim 3]
The self -compensating apparatus of an inference fringe generating position for compensating a optical path difference generated due to variation in working distance of an objective lens according to environment temperature variation in an interference lens as set forth in claim 2, wherein the interference fringe generating position adjusting part (30) includes a mounting part (32) which receives the lower outer side of the adapter (20) in the longitudinal direction and secures the interference fringe generating part (33) .
[Claim 4]
The self -compensating apparatus of an inference fringe generating position for compensating a optical path difference generated due to variation in working distance of an objective lens according to environment temperature variation in an interference lens as set forth in claim 3, wherein the interference fringe generating position adjusting part (30) further include a mounting reference part (31) which securely receives the upper outer side of the adapter (20) in the longitudinal direction and is coupled with the mounting part
(32) .
[Claim 5] The self-compensating apparatus of an inference fringe generating position for compensating a optical path difference generated due to variation in working distance of an objective lens according to environment temperature variation in an interference lens as set forth in claim 4, wherein the interference fringe generating position adjusting part (30) varies the position of the interference fringe generating part
(33) by the mounting part (32) and the mounting reference part (31) of which lengths are respectively varied in correspondence to the variation amount of the length of the barrel (11) of the objective lens (10) according to the temperature variation.
[Claim 6]
The self -compensating apparatus of an inference fringe generating position for compensating a optical path difference generated due to variation in working distance of an objective lens according to environment temperature variation in an interference lens as set forth in claim 5, wherein the mounting part (32) and the mounting reference part (31) are fastened by a screw fastening.
[Claim 7]
The self-compensating apparatus of an inference fringe generating position for compensating a optical path difference generated due to variation in working distance of an objective lens according to environment temperature variation in an interference lens as set forth in claim 5, wherein the mounting part (32) and the mounting reference part (31) are formed integrally with each other.
[Claim 8] The self-compensating apparatus of an inference fringe generating position for compensating a optical path difference generated due to variation in working distance of an objective lens according to environment temperature variation in an interference lens as set forth in any one of claims 1 to 7, wherein a material of the adapter (20) is invar or super invar having small length variation according to the temperature variation. [Claim 9]
The self -compensating apparatus of an inference fringe generating position for compensating a optical path difference generated due to variation in working distance of an objective lens according to environment temperature variation in an interference lens as set forth in claim 6, wherein, in the interference fringe generating position adjusting part (30) , an elastic means (34) is inserted between and elastically supports the mounting reference part (31) and the mounting part (32) so as to prevent a clearance due to the screw fastening of the mounting reference part (31) and the mounting part (32) . [Claim lθ]
The self -compensating apparatus of an inference fringe generating position for compensating a optical path difference generated due to variation in working distance of an objective lens according to environment temperature variation in an interference lens as set forth in claim 9, wherein the elastic means (34) is a spring.
[Claim 11]
The self -compensating apparatus of an inference fringe generating position for compensating a optical path difference generated due to variation in working distance of an objective lens according to environment temperature variation in an interference lens as set forth in claim 6 or claim 7, wherein the adapter (20) and the interference fringe generating position adjusting part (30) are respectively formed with a screw thread (21) and a screw fastening thread (35) and fastened by the screw thread (21) and the screw fastening thread (35) , and a coupling screw (40) coupled at the outside of the interference fringe generating position adjusting part (30) , and a pressurization part (41) , which has a lower strength than the screw thread (21) of the adapter (20) , is provided in the inside of the coupling screw (40) and is pressurized to the screw thread (21) of the adapter (20) and plastically deformed by the fastening of the coupling screw (40) , are further provided so as to prevent a clearance due to the screw fastening of the screw thread (21) and the screw fastening thread (35) .
[Claim 12] A self -compensating method of an inference fringe generating position for compensating a optical path difference generated due to variation in working distance of an objective lens according to environment temperature variation in an interference lens comprising the steps of: adjusting a distance between an objective lens (10) and an object (1) to be measured so as to form an image of the surface of the object (1) on the objective lens (10) ; adjusting a position of an interference fringe pattern generated by an interference fringe generating part (33) by adjusting a position of the interference fringe generating position adjusting part (30) after the adjustment of the distance between the objective lens (10) and the object (1) ; and automatically adjusting a position of the image of the surface of the object (1) and the position of the interference fringe pattern by varying the position of the interference fringe generating part (33) in response to variation in the length of the barrel (11) of the objective lens (10) according to environment temperature variation.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| KR10-2008-0001156 | 2008-01-04 | ||
| KR20080001156 | 2008-01-04 | ||
| KR10-2008-0016752 | 2008-02-25 | ||
| KR1020080016752A KR100943406B1 (en) | 2008-01-04 | 2008-02-25 | Self-compensating apparatus of Interference-Fringe-Generating position to compensate Optical Path Difference result from Objectives Lens Working Distance variation for environment temperature variation in regard of Interference Lens |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| WO2009088120A1 true WO2009088120A1 (en) | 2009-07-16 |
Family
ID=40853225
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| PCT/KR2008/001090 WO2009088120A1 (en) | 2008-01-04 | 2008-02-26 | Self-compensating apparatus of interference-fringe-generating position to compensate optical path difference result from objectives lens working distance variation for environment temperature variation in regard of interference lens |
Country Status (1)
| Country | Link |
|---|---|
| WO (1) | WO2009088120A1 (en) |
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| JP2013104998A (en) * | 2011-11-14 | 2013-05-30 | Olympus Corp | Interference objective lens |
| CN107764203A (en) * | 2017-10-27 | 2018-03-06 | 北京理工大学 | Dual wavelength phase shift interference non-spherical measuring method and device based on part penalty method |
| EP2447663B1 (en) * | 2010-10-26 | 2018-12-05 | Mitutoyo Corporation | Interference objective lens unit with temperature variation compensation and light-interference measuring apparatus using thereof |
| CN109029291A (en) * | 2018-08-16 | 2018-12-18 | 北京理工大学 | The aspherical parameter error interferometric method positioned in conjunction with laser differential confocal |
| CN110487205A (en) * | 2019-07-31 | 2019-11-22 | 北京理工大学 | In conjunction with the aspherical parameter error interferometric method of the confocal positioning of dispersion |
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| JP2003177295A (en) * | 2001-12-10 | 2003-06-27 | Sony Corp | Lens system and optical head device equipped with temperature compensating function |
| JP2003185901A (en) * | 2001-12-21 | 2003-07-03 | Konica Corp | Camera |
| US6603614B2 (en) * | 2001-01-26 | 2003-08-05 | Corning Precision Lens, Inc. | Lens assembly having automatic thermal focus adjustment |
| JP2003248171A (en) * | 2001-12-17 | 2003-09-05 | Matsushita Electric Ind Co Ltd | Variable power imaging device having temperature compensating function, and video camera |
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| US6603614B2 (en) * | 2001-01-26 | 2003-08-05 | Corning Precision Lens, Inc. | Lens assembly having automatic thermal focus adjustment |
| JP2003177295A (en) * | 2001-12-10 | 2003-06-27 | Sony Corp | Lens system and optical head device equipped with temperature compensating function |
| JP2003248171A (en) * | 2001-12-17 | 2003-09-05 | Matsushita Electric Ind Co Ltd | Variable power imaging device having temperature compensating function, and video camera |
| JP2003185901A (en) * | 2001-12-21 | 2003-07-03 | Konica Corp | Camera |
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP2447663B1 (en) * | 2010-10-26 | 2018-12-05 | Mitutoyo Corporation | Interference objective lens unit with temperature variation compensation and light-interference measuring apparatus using thereof |
| JP2013104998A (en) * | 2011-11-14 | 2013-05-30 | Olympus Corp | Interference objective lens |
| CN107764203A (en) * | 2017-10-27 | 2018-03-06 | 北京理工大学 | Dual wavelength phase shift interference non-spherical measuring method and device based on part penalty method |
| CN107764203B (en) * | 2017-10-27 | 2019-08-23 | 北京理工大学 | Dual wavelength phase shift interference non-spherical measuring method and device based on part penalty method |
| CN109029291A (en) * | 2018-08-16 | 2018-12-18 | 北京理工大学 | The aspherical parameter error interferometric method positioned in conjunction with laser differential confocal |
| CN110487205A (en) * | 2019-07-31 | 2019-11-22 | 北京理工大学 | In conjunction with the aspherical parameter error interferometric method of the confocal positioning of dispersion |
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