A dual-angle laser interferometry system

Abstract

This invention relates to the field of interferometric spectral imaging technology and discloses a dual-angle laser interferometry system, including a light source unit, an interferometry unit, a beam splitting unit, and an image acquisition unit. The light source unit emits a parallel beam to the beam splitting unit, which splits the beam. The interferometry unit includes a first sample arm, a second sample arm, and a reference arm. The beam emitted by the laser source is reflected and transmitted by the beam splitting unit to form a first beam and a second beam, respectively. The first beam and the second beam acquire a first object beam, a second object beam, and a reference beam, respectively. The image acquisition unit can acquire interferometric imaging of the sample from two perspectives based on the reference beam, the first object beam, and the second object beam. This achieves simultaneous interferometric imaging of two angles of the sample without changing the object's position, and covers twice the angle range of the sample without affecting measurement efficiency, thus expanding the application range of the interferometer.

Description

Technical Field

[0001] This invention relates to the field of interferometric spectral imaging technology, and more particularly to a dual-angle laser interferometry system. Background Technology

[0002] Interferometers have a unique advantage in resolving microscopic features. Based on the principle of light interference, interference fringes are generated. The interference fringes distributed throughout the image contain high information about the surface topography. The light reflected from the surface to be measured and the light reflected from the reference plane will form an optical path difference. Since the wavelength scale of light is on the nanometer scale, the sub-nanometer optical path difference can be resolved by the interference fringes, thus obtaining a high resolution capability of 0.1 nanometers.

[0003] However, when imaging a smooth surface, the interferometer is limited by the numerical aperture of the objective lens, resulting in a small angle of light reflection. For example, an interferometer objective lens with a magnification of 50x and a numerical aperture of 0.55 has a receiving angle of 33.4°. When using a lens with a large field of view and a small numerical aperture, the light reflection angle can be as small as less than 1°. This deficiency greatly limits the application scenarios of interferometers. To solve this problem, existing techniques measure multiple angles by rotating the interferometer or the sample. However, this method introduces micron-level motion errors, which severely reduces the measurement accuracy and significantly prolongs the measurement time. Summary of the Invention

[0004] The present invention aims to provide a dual-angle laser interferometry system, which can simultaneously perform interferometric imaging of two angles of a sample without changing the position of the object, and covers twice the angle range of the sample without affecting the measurement efficiency, thereby expanding the application range of the interferometer.

[0005] To achieve the above objectives, the basic solution of the present invention is as follows:

[0006] A dual-angle laser interferometry system includes a light source unit, an interference unit, a beam splitting unit, and an image acquisition unit. The light source unit emits a parallel beam to the beam splitting unit, and the beam splitting unit splits the beam. The interference unit includes a first sample arm, a second sample arm, and a reference arm.

[0007] The first sample arm and the second sample arm are located at two different positions on the sample to be tested, and are used to acquire the object light from two different angles of the sample to be tested.

[0008] The light source unit projects a beam of light onto the beam splitting unit. After being reflected and transmitted by the beam splitting unit, the beam of light forms a first beam and a second beam, respectively. The first beam is projected onto the sample to be tested through the first sample arm. The first beam reflected by the sample to be tested is projected onto the image acquisition unit through the beam splitting unit. The image acquisition unit acquires the first object beam of the sample to be tested.

[0009] The second beam is configured with two optical paths. In the first optical path, the second beam is reflected inside the reference arm and then projected onto the image acquisition unit, where the image acquisition unit acquires the reference beam. In the second optical path, the second beam is projected onto the sample to be tested via the second sample arm. The second beam reflected by the sample to be tested is then projected onto the image acquisition unit via the beam splitting unit, where the image acquisition unit acquires the second object beam with respect to the sample to be tested.

[0010] The image acquisition unit can acquire interference imaging of the sample under test from a first perspective based on the reference light and the first object light, and the image acquisition unit can acquire interference imaging of the sample under test from a second perspective based on the reference light and the second object light.

[0011] Furthermore, the light source unit includes a laser light source and a collimating lens group. The laser light source is a point light source. The laser light source projects a light beam onto the collimating lens group, and the light beam is then projected as a parallel light beam onto the beam splitting unit via the collimating lens group.

[0012] Furthermore, the image acquisition unit includes a camera and an eyepiece. The reference light interferes with the first object light and the second object light in the field of view of the eyepiece, and the camera acquires the interference images of the first and second viewing angles of the sample under test after interference.

[0013] Furthermore, the first sample arm includes a first objective lens, which is used to project a first light beam onto the sample to be tested and guide the first light beam reflected by the sample to the image acquisition unit via a beam splitting unit.

[0014] Furthermore, the second sample arm includes a second objective lens and a first reflector. In the second optical path of the second beam, the second beam is sequentially projected onto the sample to be tested through the first reflector and the second objective lens. After being reflected by the sample to be tested, it is sequentially guided to the image acquisition unit through the second objective lens, the first reflector, and the beam splitting unit.

[0015] Furthermore, the reference arm includes a third objective lens, a second reflecting mirror, and a piezoelectric actuator arranged in sequence. The piezoelectric actuator is used to drive the second reflecting mirror to deform, and the deformation of the second reflecting mirror can change the phase of the light beam reflected to the second reflecting mirror.

[0016] In the first optical path of the second beam, the second beam can pass through the third objective lens, be reflected by the second mirror, pass through the third objective lens, and be projected to the image acquisition unit via the beam splitting unit.

[0017] Furthermore, the beam splitting unit includes a first beam splitter, a second beam splitter, and a third beam splitter arranged in sequence, and the first beam splitter, the second beam splitter, and the third beam splitter together participate in the two optical paths of the second beam.

[0018] Furthermore, the beam splitting unit includes a first beam splitter and a second beam splitter arranged in sequence, and the first beam splitter and the second beam splitter jointly participate in the two optical paths of the second beam.

[0019] Compared with existing technologies, the advantages of this solution are:

[0020] The laser interferometer system of this scheme is equipped with two sample arms, which are located at two different positions on the sample under test. The two sample arms correspond to the same reference arm. The laser beam emitted by the laser source is reflected and transmitted by the beam splitting unit to form a first beam and a second beam, respectively. The first beam and the second beam acquire the first object beam, the second object beam, and the reference beam, respectively. The image acquisition unit can acquire interferometric imaging of the sample under test from two perspectives based on the reference beam, the first object beam, and the second object beam. Thus, it is possible to simultaneously perform interferometric imaging of the sample from two angles without changing the position of the object, and without affecting the measurement efficiency, it covers twice the angular range of the sample, which can expand the application range of the interferometer. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of Embodiment 1 of the present invention;

[0022] Figure 2 This is a schematic diagram of Embodiment 2 of the present invention.

[0023] The reference numerals in the accompanying drawings include: laser light source 1, collimating lens group 2, first beam splitter 3, camera 4, eyepiece 5, first piezoelectric actuator 6, second reflector 7, third objective lens 8, second beam splitter 9, third beam splitter 10, first objective lens 14, sample to be tested 15, second objective lens 16, and first reflector 17. Detailed Implementation

[0024] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments:

[0025] Example 1:

[0026] A dual-angle laser interferometry system, such as Figure 1 As shown, it includes a light source unit, an interference unit, a beam splitting unit, and an image acquisition unit.

[0027] The light source unit includes a laser light source 1 and a collimating lens group 2. The laser light source 1 is a point light source with good monochromaticity and a long coherence length, which can reach tens of millimeters or even meters. The laser light source 1 can project a beam onto the collimating lens group 2, and the beam is then projected as a parallel beam onto the beam splitting unit through the collimating lens group 2.

[0028] The beam splitting unit includes a first beam splitter 3, a second beam splitter 9, and a third beam splitter 10 arranged sequentially. The mirror surface of the first beam splitter 3 forms a 45° angle with the parallel beam from the collimating lens group 2. The second beam splitter 9 is arranged perpendicular to the first beam splitter 3, and the third beam splitter 10 is arranged parallel to the first beam splitter 3. The light source unit projects a beam onto the first beam splitter 3. After the beam is reflected and transmitted by the first beam splitter 3, a first beam and a second beam are formed respectively. The second beam is configured with two optical paths. The first beam splitter 3, the second beam splitter 9, and the third beam splitter 10 all participate in the two optical paths of the second beam.

[0029] The interference unit includes a first sample arm, a second sample arm, and a reference arm. The first sample arm and the second sample arm are located at two different positions of the sample to be tested 15, and are used to acquire the object light from two different angles of the sample to be tested 15.

[0030] The first sample arm includes a first objective lens 14, which is used to project a first light beam onto the sample 15 to be tested, and to guide the first light beam reflected by the sample 15 to the image acquisition unit via a beam splitting unit. The second sample arm includes a second objective lens 16 and a first reflector. In the second optical path of the second light beam, the second light beam is projected onto the sample 15 to be tested via the first reflector and the second objective lens 16 in sequence, and after being reflected by the sample 15, it is guided to the image acquisition unit via the second objective lens 16, the first reflector and the beam splitting unit in sequence.

[0031] The reference arm includes a third objective lens 8, a second reflector 7, and a piezoelectric actuator arranged in sequence. The piezoelectric actuator is used to drive the second reflector 7 to deform. The deformation of the second reflector 7 can change the phase of the light beam reflected to the second reflector 7.

[0032] The first beam is projected onto the sample 15 under test via the first sample arm. The first beam reflected by the sample 15 under test is projected onto the image acquisition unit via the beam splitting unit. The image acquisition unit acquires the first object beam about the sample 15 under test.

[0033] In the first optical path of the second beam, the second beam is reflected inside the reference arm and then projected onto the image acquisition unit, where the image acquisition unit acquires the reference light; in the second optical path of the second beam, the second beam is projected onto the sample to be tested 15 via the second sample arm, and the second beam reflected by the sample to be tested 15 is projected onto the image acquisition unit via the beam splitting unit, where the image acquisition unit acquires the second object beam with respect to the sample to be tested 15.

[0034] The image acquisition unit includes a camera 4 and an eyepiece 5. The reference light interferes with the first object light and the second object light in the field of view of the eyepiece 5. The camera 4 acquires the interference images of the first and second viewpoints of the sample 15 under test after interference.

[0035] The specific implementation method of this embodiment 1 is as follows:

[0036] The white light source is used to project a beam onto the collimating lens group 2. The beam is then projected into a parallel beam onto the first beam splitter 3 via the collimating lens group 2. The parallel beam is reflected and transmitted by the first beam splitter 3 to form a first beam and a second beam, respectively.

[0037] The first light beam is projected onto the sample 15 under test through the first objective lens 14. The first light beam reflected by the sample 15 under test is transmitted to the eyepiece 5 through the first beam splitter 3. The eyepiece 5 acquires the first object light about the sample 15 under test. In the first optical path of the second light beam, the second light beam is projected onto the second mirror 7 through the second beam splitter 9 and the third objective lens 8. After being reflected by the second mirror 7, it is projected onto the eyepiece 5 through the third objective lens 8, the second beam splitter 9 and the first beam splitter 3 in sequence. The eyepiece 5 acquires the reference light.

[0038] In the second optical path of the second beam, the second beam is projected onto the sample 15 to be tested via the second beam splitter 9, the third beam splitter 10, the first reflecting mirror, and the second objective lens 16. The second beam reflected by the sample 15 to be tested is projected onto the eyepiece 5 via the second objective lens 16, the first reflecting mirror, the third beam splitter 10, the second beam splitter 9, and the first beam splitter 3. The eyepiece 5 acquires the second object beam about the sample 15 to be tested. The reference beam interferes with the first object beam and the second object beam in the field of view of the eyepiece 5, respectively. The camera 4 acquires the interference images of the first and second viewing angles of the sample 15 to be tested after interference.

[0039] Example 2:

[0040] like Figure 2 As shown, the difference from Embodiment 1 is that in Embodiment 2, the beam splitting unit includes a first beam splitter 3 and a second beam splitter 9 arranged sequentially. The second beam splitter 9 and the first beam splitter 3 are arranged parallel to each other, and the first beam splitter 3 and the second beam splitter 9 jointly participate in the two optical paths of the second beam.

[0041] The specific implementation method of this embodiment 2 is as follows:

[0042] The white light source is used to project a beam onto the collimating lens group 2. The beam is then projected into a parallel beam onto the first beam splitter 3 via the collimating lens group 2. The parallel beam is reflected and transmitted by the first beam splitter 3 to form a first beam and a second beam, respectively.

[0043] The first light beam is projected onto the sample 15 under test through the first objective lens 14. The first light beam reflected by the sample 15 under test is transmitted to the eyepiece 5 through the first beam splitter 3. The eyepiece 5 acquires the first object light about the sample 15 under test. In the first optical path of the second light beam, the second light beam is projected onto the second mirror 7 through the second beam splitter 9 and the third objective lens 8. After being reflected by the second mirror 7, it is projected onto the eyepiece 5 through the third objective lens 8, the second beam splitter 9 and the first beam splitter 3 in sequence. The eyepiece 5 acquires the reference light.

[0044] In the second optical path of the second beam, the second beam is projected onto the sample 15 to be tested via the second beam splitter 9, the first reflecting mirror, and the second objective lens 16. The second beam reflected by the sample 15 to be tested is projected onto the eyepiece 5 via the second objective lens 16, the first reflecting mirror, the second beam splitter 9, and the first beam splitter 3. The eyepiece 5 acquires the second object beam about the sample 15 to be tested. The reference beam interferes with the first object beam and the second object beam in the field of view of the eyepiece 5, respectively. The camera 4 acquires the interference images of the first and second viewing angles of the sample 15 to be tested after interference.

[0045] The interferometric system of this scheme enables simultaneous interferometric imaging of two angles of the sample without changing the position of the object, and covers twice the angular range of the sample without affecting the measurement efficiency, thus expanding the application range of the interferometer.

[0046] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific structures and characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the structure of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A dual-angle laser interferometry system, characterized in that: The system includes a light source unit, an interference unit, a beam splitting unit, and an image acquisition unit. The light source unit emits a parallel light beam to the beam splitting unit, which splits the light beam. The interference unit includes a first sample arm, a second sample arm, and a reference arm. The first sample arm and the second sample arm are located at two different positions on the sample to be tested, and are used to acquire the object light from two different angles of the sample to be tested. The light source unit projects a light beam onto the beam splitting unit. After being reflected and transmitted by the beam splitting unit, the light beam forms a first beam and a second beam, respectively. The first beam is projected onto the sample to be tested through the first sample arm. The first beam reflected by the sample to be tested is projected onto the image acquisition unit through the beam splitting unit. The image acquisition unit acquires the first object beam about the sample to be tested. The second beam is configured to enter two optical paths simultaneously. In the first optical path, the second beam is reflected inside the reference arm and then projected onto the image acquisition unit, where the image acquisition unit acquires the reference beam. In the second optical path, the second beam is projected onto the sample to be tested via the second sample arm. The second beam reflected by the sample to be tested is then projected onto the image acquisition unit via the beam splitting unit, where the image acquisition unit acquires the second object beam with respect to the sample to be tested. The image acquisition unit can acquire interference imaging of the sample under test from a first perspective based on the reference light and the first object light, and the image acquisition unit can acquire interference imaging of the sample under test from a second perspective based on the reference light and the second object light. The beam splitting unit includes a first beam splitter, a second beam splitter, and a third beam splitter arranged in sequence. The first beam splitter, the second beam splitter, and the third beam splitter jointly participate in the two optical paths of the second beam. The mirror surface of the first beam splitter is at a 45° angle to the parallel beam from the collimating lens group. The second beam splitter is perpendicular to the first beam splitter, and the third beam splitter is parallel to the first beam splitter.

2. The dual-angle laser interferometry system according to claim 1, characterized in that: The light source unit includes a laser light source and a collimating lens group. The laser light source is a point light source. The laser light source projects a light beam onto the collimating lens group, and the light beam is then projected as a parallel light beam onto the beam splitting unit via the collimating lens group.

3. A dual-angle laser interferometry system according to claim 1, characterized in that: The image acquisition unit includes a camera and an eyepiece. The reference light interferes with the first object light and the second object light in the field of view of the eyepiece. The camera acquires the interference images of the sample under test from the first and second viewing angles after interference.

4. The dual-angle laser interferometry system according to claim 1, characterized in that: The first sample arm includes a first objective lens, which is used to project a first light beam onto the sample to be tested and to guide the first light beam reflected by the sample to the image acquisition unit via a beam splitting unit.

5. A dual-angle laser interferometry system according to claim 1, characterized in that: The second sample arm includes a second objective lens and a first reflector. In the second optical path of the second beam, the second beam is directed toward the sample to be tested via the first reflector and the second objective lens in sequence. After being reflected by the sample to be tested, the beam is directed toward the image acquisition unit via the second objective lens, the first reflector, and the beam splitting unit in sequence.

6. The dual-angle laser interferometry system according to claim 1, characterized in that: The reference arm includes a third objective lens, a second reflector, and a piezoelectric actuator arranged in sequence. The piezoelectric actuator is used to drive the second reflector to deform, and the deformation of the second reflector can change the phase of the light beam reflected to the second reflector. In the first optical path of the second beam, the second beam can pass through the third objective lens, be reflected by the second mirror, pass through the third objective lens, and be projected to the image acquisition unit via the beam splitting unit.

Images