CN118011653A - Focal length fine adjustment device suitable for Mirau objective lens reference reflector - Google Patents
Focal length fine adjustment device suitable for Mirau objective lens reference reflector Download PDFInfo
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- CN118011653A CN118011653A CN202410163295.8A CN202410163295A CN118011653A CN 118011653 A CN118011653 A CN 118011653A CN 202410163295 A CN202410163295 A CN 202410163295A CN 118011653 A CN118011653 A CN 118011653A
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- 230000010287 polarization Effects 0.000 claims abstract description 50
- 230000003287 optical effect Effects 0.000 abstract description 14
- 238000005259 measurement Methods 0.000 abstract description 7
- 230000009286 beneficial effect Effects 0.000 abstract description 2
- 241000219739 Lens Species 0.000 description 29
- 238000003384 imaging method Methods 0.000 description 4
- 230000001678 irradiating effect Effects 0.000 description 3
- 210000001747 pupil Anatomy 0.000 description 3
- 238000004026 adhesive bonding Methods 0.000 description 2
- 239000003822 epoxy resin Substances 0.000 description 2
- 238000005286 illumination Methods 0.000 description 2
- 238000005305 interferometry Methods 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 229920000647 polyepoxide Polymers 0.000 description 2
- 239000000853 adhesive Substances 0.000 description 1
- 230000001070 adhesive effect Effects 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
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- 238000005516 engineering process Methods 0.000 description 1
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Abstract
The application discloses a focal length fine adjustment device suitable for a Mirau objective lens reference reflector, and belongs to the field of optical device design. Comprising the following steps: the first photosensitive member includes a light source; an interference objective lens is arranged below the first photosensitive member; the polarization beam splitter is inclined relative to the horizontal plane, the polarization beam splitter divides light into s light and p light, the p light passes through the polarization beam splitter to be irradiated on the surface of an object to be measured, a first analyzer and a reflecting mirror are arranged on the right side of the polarization beam splitter, the first analyzer and the reflecting mirror are perpendicular to the horizontal plane, the reflecting mirror faces the surface of the first analyzer to form a reference plane, and the s light passes through the first analyzer to be irradiated on the reference plane of the reflecting mirror. The application has the beneficial effects that: the focus fine adjustment device for the Mirau objective lens reference reflector can adjust the energy of s light transmitted by the analyzer, so that the optimal contrast of the s light relative to p light is realized, and the measurement accuracy is improved.
Description
Technical Field
The application relates to the field of optical device design, in particular to a focal length fine adjustment device suitable for a Mirau objective lens reference reflector.
Background
In the traditional Mirau objective, a half reflecting mirror is arranged in the middle of the objective, which is away from the surface to be measured, then a reflecting mirror is arranged at the exit pupil of the objective, and light rays are incident on the surface of the object to be measured in a converging illumination mode through the interference objective. Because the light splitting proportion is fixed, the light intensity proportion of the measuring light and the reference light cannot be adjusted, and the optimal light intensity contrast requirement cannot be achieved for different reflecting surfaces, so that the measuring precision is affected.
Disclosure of Invention
The summary of the application is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. The summary of the application is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
To solve the technical problems mentioned in the background section above, some embodiments of the present application provide a focal length fine adjustment device suitable for Mirau objective lens reference mirror, including: the first photosensitive member comprises a light source which emits light downwards; an interference objective lens is arranged below the first photosensitive element, and light passes through the interference objective lens; the interference objective lens is characterized in that a polarization beam splitter is arranged below the interference objective lens and is inclined relative to a horizontal plane, the polarization beam splitter divides light into s light and p light, the p light passes through the polarization beam splitter to irradiate on the surface of a measured object, a first polarization analyzer and a reflecting mirror are arranged on the right side of the polarization beam splitter, the first polarization analyzer and the reflecting mirror are perpendicular to the horizontal plane, the reflecting mirror faces the surface of the first polarization analyzer to form a reference plane, and the s light passes through the first polarization analyzer to irradiate on the reference plane of the reflecting mirror.
Further, a second photosensitive member and a second analyzer are arranged between the first photosensitive member and the interference objective lens, a first photosensitive surface is formed on the lower surface of the first photosensitive member, a second photosensitive surface is formed on the second photosensitive member, and an included angle of 90 degrees is formed between the first photosensitive surface and the second photosensitive surface; the second analyzer is located between the first photosurface and the second photosurface.
Further, an interference objective sleeve is arranged on the interference objective, and the interference objective is arranged in the interference objective sleeve; the polarization beam splitter is provided with a rotating structure, the rotating structure enables the polarization beam splitter, the first polarization analyzer and the reflecting mirror to rotate around the central axis of the rotating structure, and the central axis of the rotating structure is parallel to and deviated from the central axis of the interference objective lens.
Further, the amount of deviation of the central axis of the rotating structure from the central axis of the interference objective lens is greater than the white light coherence length.
Further, the interference objective includes a plurality of side-by-side lenses.
Further, the first photosurface and the second photosurface are arranged in mirror image relative to the second analyzer.
Further, the rotating structure can rotate 360 degrees on the horizontal plane.
Further, the photosensitive element of the first photosensitive member and the photosensitive element of the second photosensitive member are one of CCD, CMOS, exmor R CMOS, and the like.
The application has the beneficial effects that:
The light emitted from the first photosensitive element passes through the interference objective lens to reach the polarizing beam splitter, the polarizing beam splitter divides the light into s light and p light, the p light passes through the polarizing beam splitter to irradiate the surface of the measured object and returns to the first photosensitive element along the original path, the s light passes through the first polarization beam splitter to irradiate the reflecting mirror and returns to the first photosensitive element along the original path, and the polarization beam splitter can adjust the energy of the s light transmitted by itself, thereby realizing the optimal contrast of the s light relative to the p light and improving the measurement accuracy.
Drawings
The accompanying drawings, which are included to provide a further understanding of the application, are incorporated in and constitute a part of this specification. The drawings and their description are illustrative of the application and are not to be construed as unduly limiting the application.
In addition, the same or similar reference numerals denote the same or similar elements throughout the drawings. It should be understood that the figures are schematic and that elements and components are not necessarily drawn to scale.
In the drawings:
FIG. 1 is an overall schematic of an embodiment according to the present application;
fig. 2 is a schematic structural diagram of a conventional Mirau interference objective lens.
Reference numerals:
1. a first photosensitive member; 2. an interference objective; 3. a polarizing beam splitter; 4. a first analyzer; 5. a reflecting mirror; 6. a second analyzer; 7. a second photosensitive member; 8. an interference objective jacket; 9. a rotating structure; 10. the surface of the object to be measured; 11. semi-reflective semi-transparent lens.
Detailed Description
Embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While certain embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete. It should be understood that the drawings and embodiments of the present disclosure are for illustration purposes only and are not intended to limit the scope of the present disclosure.
It should be noted that, for convenience of description, only the portions related to the present invention are shown in the drawings. Embodiments of the present disclosure and features of embodiments may be combined with each other without conflict.
It should be noted that the terms "first," "second," and the like in this disclosure are merely used to distinguish between different devices, modules, or units and are not used to define an order or interdependence of functions performed by the devices, modules, or units.
It should be noted that references to "one", "a plurality" and "a plurality" in this disclosure are intended to be illustrative rather than limiting, and those of ordinary skill in the art will appreciate that "one or more" is intended to be understood as "one or more" unless the context clearly indicates otherwise.
The present disclosure will be described in detail below with reference to the accompanying drawings in conjunction with embodiments.
With reference to figures 1-2 of the drawings,
A focal length fine tuning device for Mirau objective lens reference mirror 5, comprising: a first photosensitive member 1, an interference objective lens 2, a polarization beam splitter 3, a first analyzer 4, and a reflecting mirror 5. The first photosensitive member 1 is a camera, and the photosensitive element of the first photosensitive member 1 is one of a CCD, CMOS, exmor R CMOS, and the like, preferably CMOS having high sensitivity and short exposure time. The first photosensitive member 1 includes a light source located below the first photosensitive member 1 for emitting white light downward. The interference objective 2 is located under the light source on the first photosensitive member 1, and the interference objective 2 is a convex lens with four main optical axes coincident and arranged from top to bottom, and is used for gathering the divergent white light emitted by the first photosensitive member 1. The polarization beam splitter 3 is located directly below the interference objective lens 2, the polarization beam splitter 3 is one of a PSB or other polarization beam splitting components, in this embodiment, the PSB is selected, the polarization beam splitter 3 forms an included angle with respect to a horizontal plane, the included angle ranges from 10 degrees to 60 degrees, the polarization beam splitter 3 is used for dividing white light passing through the interference objective lens 2 into p light passing through the polarization beam splitter 3 and irradiating on a surface 10 of a measured object and s light reflected on the polarization beam splitter 3, the surface 10 of the measured object is located directly below the polarization beam splitter 3, a first photosurface is formed below the first photosurface, and the p light is reflected after irradiating on the surface 10 of the measured object. The first analyzer 4 is formed by combining a plurality of polarizers, the reflecting mirror 5 is a plane mirror, the mirror surfaces of the first analyzer 4 and the reflecting mirror 5 are perpendicular to the horizontal plane and face the polarizing beam splitter 3, the mirror surface of the reflecting mirror 5 facing the polarizing beam splitter 3 forms a reference plane, and s light is reflected from the polarizing beam splitter 3 after passing through the first analyzer 4 and irradiating the reflecting mirror 5. The main optical axis of the first analyzer 4 can be adjusted to change the energy of s-light transmitted through the analyzer, the main optical axis is a common concept in the optical field, and the contrast of the s-light with changed energy is higher when compared with p-light, so that the measurement accuracy is improved.
Specifically, a second analyzer 6 and a second photosensitive member 7 are disposed between the first photosensitive member 1 and the interference objective lens 2, the second analyzer 6 is composed of a plurality of polarizing plates, and the second photosensitive member 7 is a camera whose photosensitive element is CMOS. The second photosensitive member 7 is formed with a second photosensitive plane perpendicular to the horizontal plane, the second analyzer 6 is located between the first photosensitive member 1 and the second photosensitive member 7, the first photosensitive plane and the second photosensitive plane are arranged in mirror image with respect to the mirror surface of the second analyzer 6, and an included angle between the first photosensitive plane and the second photosensitive plane is 90 °.
Specifically, the interference objective 2 is provided with an outer sleeve of the interference objective 2, the outer sleeve of the interference objective 2 is cylindrical, the interference objective 2 is fixed in the outer sleeve of the interference objective 2 through gluing, and the gluing agent can be epoxy resin, ulipendan adhesive or the like, and in the embodiment, the epoxy resin is selected. The polarization beam splitter 3 is provided with a rotating structure 9, the rotating structure 9 is a cylindrical shell, the polarization beam splitter 3 and the reflecting mirror 5 are fixedly connected to the rotating structure 9, and the first analyzer 4 is rotationally connected with the rotating structure 9, so that the first analyzer 4 can rotate around a main optical axis of the first analyzer 4, and the main optical axis of the first analyzer 4 is parallel to a horizontal plane. The rotating structure 9 makes the polarization beam splitter 3, the first polarization analyzer 4 and the reflecting mirror 5 rotate 360 ° around the central axis of the rotating structure 9 in the horizontal plane, the central axis of the rotating structure 9 is parallel to the central axis of the outer sleeve of the interference objective lens 2 and has a deviation amount, the deviation amount is larger than the white light coherence length, the rotating structure 9 is rotated to realize the optimal white light interferometry, and the white light coherence length is a common concept in the optical field.
The working process comprises the following steps: the light source on the first photosensitive member 1 emits white light, which is irradiated on the polarization beam splitter 3 through the second analyzer 6 and the interference objective lens 2, and the polarization beam splitter 3 splits the white light into p-light and s-light. The p light passes through the polarization beam splitter 3 along the advancing direction of the white light and irradiates on the surface 10 of the object to be measured, the p light is reflected on the surface 10 of the object to be measured and irradiates on the second analyzer 6 through the polarization beam splitter 3 and the interference objective lens 2, the second analyzer 6 divides the p light into two beams, one beam irradiates on the first photosurface through the second analyzer 6, and the other beam irradiates on the second photosurface after being reflected by the second analyzer 6. The s-light passes through the first analyzer 4 from the polarization beam splitter 3 and irradiates the reflecting mirror 5, and the s-light is reflected by the reflecting mirror 5 and then irradiates the second analyzer 6 along the first analyzer 4, the polarization beam splitter 3 and the interference objective lens 2, and the s-light is also divided into two beams by the second analyzer 6 and irradiates the light sensitive surface and the second light sensitive surface respectively.
When the s-ray energy passing through the first analyzer 4 is too large and too small, the main optical axis of the analyzer is rotated to adjust the light intensity of the s-ray, so as to realize the optimal contrast ratio of the s-ray and the p-ray, thereby improving the measurement accuracy.
The central axis of the rotating structure 9 has a deviation amount with the central axis of the outer sleeve of the interference objective lens 2, and the rotating structure 9 rotates the polarization beam splitter 3, the first polarization analyzer 4 and the reflecting mirror 5 around the central axis of the rotating structure 9, so that fine adjustment of the optical path of s light is realized, and optimal white light interferometry is realized.
The conventional Mirau interference objective 2 is shown in fig. 2, and light is incident on the surface of the object to be measured through the interference objective 2 in a converging illumination manner, and it is assumed that the microscopic imaging system with the interference objective 2 is already in the best focus position. At half the distance between the surface of the object to be measured and the exit pupil of the interference objective 2, there is a half mirror 11, which reflects part of the light transmitted from the interference objective 2 and then makes it incident on the reference plane of the mirror 5 (the mirror 5 at the exit pupil of the interference objective 2 in the figure), and the other part of the light is transmitted through the half mirror 11 and then makes it incident on the surface 10 of the object to be measured.
The light rays incident on the reflector 5 return to the microscopic imaging system along the original path after passing through the reflector 5 and are used as reference light for interference imaging; light incident on the surface 10 of the object to be measured is reflected and/or scattered by the surface, and then enters the microscopic imaging system to interfere with the reference light to form an interference image on the image plane of the camera.
The advantage of this construction is compactness, with only half the working distance lost. For larger magnification objective systems, it is reasonable, but the disadvantages are: 1) Because the light splitting proportion is fixed, the light intensity proportion of the measuring light and the reference light cannot be adjusted, and the optimal light intensity contrast requirements for different reflecting surfaces cannot be met, so that the measuring precision is affected; 2) The reference mirror surface distance cannot be finely adjusted, after the objective lens leaves the factory, if the optimal focusing distance and the zero optical path difference position have deviation, the adjustment cannot be carried out again, or the direct distance between the microscope objective lens system and the camera has slight error, so that when the focusing distance slightly deviates from the optimal distance adjusted by the microscope objective lens, the optimal interference fringe contrast and the optimal focusing cannot be simultaneously realized.
The structure of the focal length fine adjustment device suitable for the Mirau objective lens reference mirror 5 in this embodiment is shown in fig. 1, and the working procedure is as described above, and the advantage thereof is that: 1) The data measured by the first photosensitive member 1 and the second photosensitive member 7 can be compared, eliminating some errors in the measurement. Because the reflection or scattering of the surface of the measured object is determined by the surface characteristics, the adjustment of the light intensity of the reference light can effectively balance the reference light and the measuring light, and the optimal contrast is realized, so that the measuring precision is improved; 2) The mirror 5, the polarizing beam splitter 3 is mounted on a rotating structure 9 rotatable along the envelope of the interference objective 2, such that the central axis of the rotating structure 9 is parallel to the central axis of the envelope of the interference objective 2, but with a small amount of deviation, which may cover the coherence length of the interference, corresponding to a typical white light interference, which is a few microns. The adjustment quantity of a few micrometers is adjusted in a rotating 360-degree range through two devices with slightly deviated centers, so that very high-precision controllable adjustment can be realized, and the optimal focusing position and the optimal interference position (zero optical path position) of the interference microscope are completely overlapped, and the optimal measurement effect is achieved; 3) Since the polarization states of the s-light and the p-light returned from the object surface and the reference surface are orthogonal, a second analyzer 6 is placed in the optical path, and the second analyzer 6 causes the s-light and the p-light to simultaneously form interference on the first photosurface and the second photosurface, forming two interference images. The two interference images can be mutually referenced, so that measurement errors possibly caused by interference of factors such as environmental vibration can be eliminated to a certain extent.
The foregoing description is only of the preferred embodiments of the present disclosure and description of the principles of the technology being employed. It will be appreciated by those skilled in the art that the scope of the invention in the embodiments of the present disclosure is not limited to the specific combination of the above technical features, but encompasses other technical features formed by any combination of the above technical features or their equivalents without departing from the spirit of the invention. Such as the above-described features, are mutually substituted with (but not limited to) the features having similar functions disclosed in the embodiments of the present disclosure.
Claims (8)
1. A focal length fine tuning device for a Mirau objective lens reference mirror, comprising: the first photosensitive member comprises a light source which emits light downwards; an interference objective lens is arranged below the first photosensitive element, and light passes through the interference objective lens; the interference objective lens is characterized in that a polarization beam splitter is arranged below the interference objective lens and is inclined relative to a horizontal plane, the polarization beam splitter divides light into s light and p light, the p light passes through the polarization beam splitter to irradiate on the surface of a measured object, a first polarization analyzer and a reflecting mirror are arranged on the right side of the polarization beam splitter, the first polarization analyzer and the reflecting mirror are perpendicular to the horizontal plane, the reflecting mirror faces the surface of the first polarization analyzer to form a reference plane, and the s light passes through the first polarization analyzer to irradiate on the reference plane of the reflecting mirror.
2. The focal length fine tuning device for Mirau objective reference mirrors according to claim 1, wherein:
A second photosensitive member and a second analyzer are arranged between the first photosensitive member and the interference objective lens, a first photosensitive surface is formed on the lower surface of the first photosensitive member, a second photosensitive surface is formed on the second photosensitive member, and an included angle of 90 degrees is formed between the first photosensitive surface and the second photosensitive surface; the second analyzer is located between the first photosurface and the second photosurface.
3. The focal length fine tuning device for Mirau objective reference mirrors according to claim 1, wherein:
An interference objective sleeve is arranged on the interference objective, and the interference objective is arranged in the interference objective sleeve; the polarization beam splitter is provided with a rotating structure, the rotating structure enables the polarization beam splitter, the first polarization analyzer and the reflecting mirror to rotate around the central axis of the rotating structure, and the central axis of the rotating structure is parallel to and deviated from the central axis of the interference objective lens.
4. A focal length fine tuning apparatus for Mirau objective reference mirrors according to claim 3, wherein:
the deviation of the central axis of the rotating structure from the central axis of the interference objective lens is larger than the coherence length of white light.
5. A focal length fine tuning apparatus for Mirau objective lens reference mirror according to claims 1-3, characterized in that:
the interference objective includes a plurality of side-by-side lenses.
6. The focal length fine tuning device for Mirau objective reference mirrors according to claim 2, wherein:
the first photosurface and the second photosurface are arranged in mirror image relative to the second analyzer.
7. A focal length fine tuning apparatus for Mirau objective reference mirrors according to claim 3, wherein:
the rotating structure can rotate 360 degrees on the horizontal plane.
8. A focal length fine tuning apparatus for Mirau objective lens reference mirror according to claims 1-3, characterized in that:
The photosensitive element of the first photosensitive member and the photosensitive element of the second photosensitive member are each one of a CCD, CMOS, exmor R CMOS, and the like.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202410163295.8A CN118011653A (en) | 2024-02-05 | 2024-02-05 | Focal length fine adjustment device suitable for Mirau objective lens reference reflector |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202410163295.8A CN118011653A (en) | 2024-02-05 | 2024-02-05 | Focal length fine adjustment device suitable for Mirau objective lens reference reflector |
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| Publication Number | Publication Date |
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| CN118011653A true CN118011653A (en) | 2024-05-10 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN202410163295.8A Pending CN118011653A (en) | 2024-02-05 | 2024-02-05 | Focal length fine adjustment device suitable for Mirau objective lens reference reflector |
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| CN (1) | CN118011653A (en) |
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- 2024-02-05 CN CN202410163295.8A patent/CN118011653A/en active Pending
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