Rapid focusing method of white light interferometer

Abstract

The invention discloses a quick focusing method of a white light interferometer, which comprises the following steps of: focusing an interference objective lens module at a first position, projecting a detection light beam towards an object to be detected to generate a first interference light beam, and receiving and analyzing a first interference spectrum by a spectrum light receiving module, the interference objective lens module is focused at a second position along a scanning direction, so that a second interference light beam is generated after the detection light beam is projected on the object to be detected, and a second interference spectrum is generated according to the second interference light beam; a spectrum analysis module is used for analyzing the first interference spectrum and the second interference spectrum to generate a first defocus distance and a second defocus distance respectively, then an optimal focusing position is calculated, and finally the interference objective lens module is adjusted to be focused at the optimal focusing position.

Description

Technical Field

[0001] The present invention relates to a rapid focusing method for a white light interferometer, and particularly to a rapid focusing method for a white light interferometer that analyzes the optimal focusing position using interference spectroscopy. Background Art

[0002] In some extremely precise processing or manufacturing fields such as micrometers or nanometers, in order to measure the three-dimensional microscopic topography of an object, a white light interferometer is usually used for measurement.

[0003] Please refer to Figure 1 , Figure 1 which is a schematic diagram of the system architecture of an existing white light interferometer. As Figure 1 shown, a white light interferometer PA100 includes a light source PA1, a beam splitter PA2, an interference objective lens module PA3, and an image capture device PA4; among them, the interference objective lens module PA3 includes a convex lens PA31, a beam splitter PA32, and a reference mirror PA33.

[0004] As described above, the principle used by the white light interferometer PA100 is mainly to split the beam provided by the light source PA1 into two beams by the beam splitter PA32. One beam will pass through the beam splitter PA32 and be projected onto a test object PA200, and the other beam will be reflected to the reference mirror PA33. Therefore, the beam reflected from the test object PA200 will converge with the beam reflected from the reference mirror PA33, thereby causing interference fringes to appear in the image captured by the image capture device PA4, and the relative height of the surface of the test object PA200 can be analyzed through the position of the interference fringes.

[0005] In actual operation, since the white light interferometer PA100 focuses by vertical scanning technology and then analyzes the captured images, there are problems of low accuracy and slow speed. Summary of the Invention

[0006] In view of the fact that in the prior art, existing white light interferometers mainly obtain multiple images through vertical scanning technology and then analyze the focusing position through image analysis. Therefore, it often takes a long time, and only an approximate focusing position can be known through the resolution by image analysis, so there is also a problem of low accuracy; therefore, the main object of the present invention is to provide a rapid focusing method for a white light interferometer, which can perform focusing quickly and accurately through simple steps.

[0007] The present invention solves the problems of the prior art. The necessary technical means adopted by the present invention is to provide a fast focusing method of a white light interferometer, which is applied to a white light interferometer having a spectral light receiving module and is implemented in combination with a spectral analysis module. The white light interferometer has an interference objective lens module and is provided with a spectral interference technology working range. The spectral analysis module has an analysis misalignment distance interval. The fast focusing method of the white light interferometer includes the following steps (A) to (G).

[0008] Step (A) is to set the focal length of the interference lens module to a first position within the working range of the spectral interference technology. Step (B) is to project a detection beam toward an object to be tested through the interference lens module, so that the detection beam is reflected from the object to be tested to form a first reflected beam, so that after the interference lens module receives the first reflected beam, interference is formed to generate a first interference beam, and then the first interference beam is received by the spectrum receiving module and analyzed to obtain a first interference spectrum.

[0009] Step (C) is to move the focal length of the interference objective lens module along a scanning direction to a second position within the working range of the spectral interference technology by a scanning movement amount, and the scanning movement amount is greater than or equal to the analytical misalignment distance interval.

[0010] Step (D) is to project a detection beam toward the object to be tested through the interference objective lens module, so that the detection beam is reflected from the object to be tested to produce a second reflected beam, so that after the interference objective lens module receives the second reflected beam, interference is formed to generate a second interference beam, and then the second interference beam is received by the spectrum receiving module and analyzed to produce a second interference spectrum.

[0011] In step (E), a spectrum analysis module is used to analyze the first interference spectrum and the second interference spectrum to generate a first defocus distance and a second defocus distance respectively.

[0012] Step (F) is to increase the first position by the first defocus distance along the scanning direction to serve as an optimal focusing position when the first defocus distance is greater than or equal to the second defocus distance; and to increase the second defocus distance from the second position along the direction opposite to the scanning direction to serve as an optimal focusing position when the first defocus distance is less than the second defocus distance.

[0013] Step (G) is to adjust the focal length of the interference objective lens module to the optimal focusing position.

[0014] In an auxiliary technical means derived from the above necessary technical means, the interference objective lens module is a Mirau interference objective lens module, a Michelson interference objective lens module or a Linnik interference objective lens module.

[0015] As described above, the present invention mainly calculates the optimal focusing position by using the interference spectra obtained at different scanning positions, and then the interference objective lens module can be directly focused on the optimal focusing position, which is very fast and convenient, and the focusing accuracy is also very high.

[0016] Specific embodiments adopted by the present invention will be further described through the following embodiments and accompanying drawings. Description of the Drawings

[0017] Figure 1 is a schematic diagram of the system architecture of an existing white light interferometer;

[0018] Figure 2 is a system architecture diagram of the white light interferometer to which the fast focusing method of the white light interferometer of the present invention is applied;

[0019] Figure 3 is a system architecture diagram of another white light interferometer to which the fast focusing method of the white light interferometer of the present invention is applied;

[0020] Figure 4 is a partially enlarged schematic diagram of the white light interferometer to which the fast focusing method of the white light interferometer of the present invention is applied;

[0021] Figure 5 is a conversion comparison schematic diagram showing the conversion of the wavelength of the interference spectrum to the defocus distance;

[0022] Figure 6 is a conversion comparison schematic diagram showing the conversion of the wavelength of the interference spectrum to the defocus distance;

[0023] Figure 7 is a conversion comparison schematic diagram showing the conversion of the wavelength of the interference spectrum to the defocus distance;

[0024] Figure 8 is a comparison schematic diagram of the scanning position and the focusing position measured by using the fast focusing method of the white light interferometer provided by the preferred embodiment of the present invention;

[0025] Figure 9 is a comparison schematic diagram of the difference between the first scanning position and the second scanning position measured by using the fast focusing method of the white light interferometer provided by the preferred embodiment of the present invention compared with the parsing misalignment distance interval of the spectrum analysis module; and

[0026] Figure 10 is a comparison schematic diagram of another scanning position and the focusing position measured by using the fast focusing method of the white light interferometer provided by the preferred embodiment of the present invention;

[0027] Among them, reference numerals:

[0028] PA100: White light interferometer;

[0029] PA1: Light source;

[0030] PA2: Beam splitter;

[0031] PA3: Interference objective lens module;

[0032] PA31: Convex lens;

[0033] PA32: Beam splitter;

[0034] PA33: Reference mirror;

[0035] PA4: Image capture device;

[0036] PA200: Object to be measured;

[0037] 100, 100a: White light interferometer;

[0038] 1: Base;

[0039] 11: Housing body;

[0040] 12, 13, 15: Convex lens;

[0041] 14: Beam splitter;

[0042] 2: White light source;

[0043] 3: Interference objective lens module;

[0044] 31: Lens barrel;

[0045] 32: Focusing lens;

[0046] 33: Beam splitter;

[0047] 34: Reference mirror;

[0048] 4: Image capture device;

[0049] 5, 5a: Spectral light collection module;

[0050] 51, 51a: Beam splitter;

[0051] 52: Convex lens;

[0052] 53, 53a: Fiber optic cable light collector;

[0053] 54, 54a: Spectrometer;

[0054] 6: Spectral analysis module;

[0055] 200: Object to be measured;

[0056] 201: Groove;

[0057] WB: Detection beam;

[0058] IB: Interference beam;

[0059] SR: Working range of spectral interference technology;

[0060] Z0, Z1, Z2: Focus positions;

[0061] A, A1, A2, A3: First positions;

[0062] B, B1, B2, B3: Second positions;

[0063] a, a1, a2, a3: First defocus distances;

[0064] b, b1, b2, b3: Second defocus distances;

[0065] c: Difference value;

[0066] AR: Analytical misalignment distance range;

[0067] D1: Scanning direction;

[0068] BF: Best focus position. Detailed implementation manner

[0069] Please refer to Figure 2 , Figure 2 which is a system architecture diagram of a white light interferometer to which the fast focusing method of the white light interferometer of the present invention is applied. As Figure 2 shown, a fast focusing method of a white light interferometer provided in this embodiment is applied to a white light interferometer 100, and the white light interferometer 100 includes a base 1, a white light source 2, an interference objective lens module 3, an image capturing device 4, a spectral light collecting module 5, and a spectral analysis module 6.

[0070] The base 1 includes a housing body 11, a convex lens 12, a convex lens 13, a beam splitter 14, and a convex lens 15; wherein, the convex lenses 12, 13, and 15 and the beam splitter 14 are actually installed and fixed through the fixing structure of the housing body 11 itself, thereby forming an optical path within the housing body 11. And since the arrangement manners of the convex lenses 12, 13, and 15 and the beam splitter 14 are common in general optical detection devices, and their specific positions can be known from the beam traveling path and the attached drawings described later, their detailed structures are not elaborated herein.

[0071] The white light source 2 is disposed within the housing body 11 to provide a detection light beam WB. The above-mentioned convex lenses 12 and 13 and the beam splitter 14 are disposed on the projection path of the white light source 2, such that the detection light beam WB projected by the white light source 2 will sequentially pass through the convex lenses 12 and 13 to form a parallel light beam with a larger diameter, and then be projected onto the beam splitter 14. Among them, the convex lenses 12 and 13 magnify the detection light beam WB according to a specific size ratio, and the mirror surface of the beam splitter 14 is maintained at 45 degrees with respect to the projection direction of the detection light beam WB. However, these are all common technical contents in the optical field, so they will not be elaborated here.

[0072] The interference objective lens module 3 includes a lens barrel 31, a focusing lens 32, a beam splitter 33, and a reference mirror 34. The lens barrel 31 is fixed to the housing body 11 and corresponds to the beam splitter 14. The focusing lens 32 is disposed within the lens barrel 31 and corresponds to the splitting path of the beam splitter 14 to receive the detection light beam WB reflected by the beam splitter 14. The beam splitter 33 is spaced apart from the focusing lens 32 to allow the detection light beam WB focused by the focusing lens 32 to pass through and be reflected. Among them, the detection light beam WB that passes through the beam splitter 33 after being focused by the focusing lens 32 is used to be focused on a measurement object 200 and is reflected from the measurement object 200 to form a reflected light beam. The reference mirror 34 is disposed between the focusing lens 32 and the beam splitter 33 to reflect the detection light beam WB reflected by the beam splitter 33 back to the beam splitter 33, thereby generating interference with the reflected light beam reflected from the measurement object 200 to form an interference light beam IB, and causing the interference light beam IB to be projected onto the beam splitter 14. When the interference light beam IB is projected onto the beam splitter 14, it will also be split by the beam splitter 14 and projected towards the white light source 2 and the image capturing device 4 respectively.

[0073] In addition, although in this embodiment, the interference objective lens module 3 is a Mirau type interference objective lens module, it is not limited thereto. In other embodiments, the interference objective lens module 3 may also be a Michelson type interference objective lens module or a Linnik type interference objective lens module.

[0074] The image capturing device 4 is disposed within the housing body 11 and is used to receive the interference light beam IB that is split by the beam splitter 14 and projected towards the image capturing device 4. Before the interference light beam IB enters the image capturing device 4, it will be focused by the convex lens 15. Specifically, the image capturing device 4 is, for example, a Charge-coupled Device (CCD).

[0075] The spectral light collection module 5 includes a beam splitter 51, a convex lens 52, an optical fiber cable light collector 53, and a spectrometer 54. The beam splitter 51 is disposed between the beam splitter 14 and the convex lens 15 to further split the interference beam IB passing through the beam splitter 14. Therefore, the interference beam IB captured by the image capturing device 4 is actually the interference beam IB after being split by the beam splitter 51. The convex lens 52 is disposed on the other side of the beam splitter 51 relative to the convex lens 15 to receive another interference beam IB split by the beam splitter 51. The optical fiber cable light collector 53 is disposed on the other side of the convex lens 52 relative to the beam splitter 51 to receive the interference beam IB focused by the convex lens 52. The spectrometer 54 is connected to the optical fiber cable light collector 53 through an optical fiber cable to generate an interference spectrum based on the interference beam IB received by the optical fiber cable light collector 53.

[0076] The spectral analysis module 6 is electrically connected to the spectrometer 54 to analyze the interference spectrum generated by the spectrometer 54. Specifically, the spectral analysis module 6 is, for example, a spectral analysis software installed in a computer host.

[0077] Please continue to refer to Figure 3 , Figure 3 which is a system architecture diagram of another white light interferometer to which the fast focusing method of the white light interferometer of the present invention is applied. As Figure 2 and Figure 3 shown, the fast focusing method of the white light interferometer of the present invention can also be applied to another white light interferometer 100a, and the white light interferometer 100a replaces the spectral light collection module 5 of the white light interferometer 100 with a spectral light collection module 5a; wherein, the spectral light collection module 5a includes a beam splitter 51a, an optical fiber cable light collector 53a, and a spectrometer 54a. The beam splitter 51a is disposed between the convex lens 15 and the image capturing device 4. Therefore, the interference beam IB received by the beam splitter 51a is the interference beam IB that has been focused by the convex lens 15. Therefore, the interference beam IB after being split by the beam splitter 51a can be directly projected onto the optical fiber cable light collector 53a, so that the spectrometer 54a generates an interference spectrum based on the interference beam IB, and the spectral analysis module 6 electrically connected to the spectrometer 54a analyzes the interference spectrum accordingly.

[0078] Please continue to refer to Figure 4 , Figure 4 which is a partially enlarged schematic diagram of the white light interferometer to which the fast focusing method of the white light interferometer of the present invention is applied. As Figure 2 and Figure 4 shown, the interference objective lens module 3 has a default spectral interference technology working range SR, and the interference objective lens module 3 can focus on a groove 201 of a test object 200 within the spectral interference technology working range SR.

[0079] Please continue to refer to Figure 5 , Figure 5 which is a conversion comparison schematic diagram showing the conversion of the wavelength of the interference spectrum to the defocus distance. As Figure 2 , Figure 4 and Figure 5 shown, when the interference objective lens module 3 focuses on a test object 200 at a focusing position Z0, it will correspondingly generate an interference beam IB. Then, after the spectral light collection module 5 collects the light to generate an interference spectrum, the spectral analysis module 6 will first convert the wavelength in the interference spectrum to a wave number, and then convert it to a defocus distance through Fourier transform. This is known to those with ordinary knowledge in the technical field, so it will not be elaborated further here; among them, the intensity corresponding to the focusing position Z0 is concentrated at the position where the defocus distance approaches 0, which means that the focusing position Z0 approaches the best focusing position of the groove 201 of the test object 200.

[0080] Please continue to refer to Figure 6 , Figure 6 which is a conversion comparison schematic diagram showing the conversion of the wavelength of the interference spectrum to the defocus distance. As Figure 2 , Figure 4 and Figure 6 shown, when the interference objective lens module 3 focuses on a test object 200 at a focusing position Z1, it will correspondingly generate an interference beam IB. Then, after the spectral light collection module 5 collects the light to generate an interference spectrum, it will also be converted to a defocus distance through the spectral analysis module 6; among them, the intensity corresponding to the focusing position Z1 is concentrated at the position where the defocus distance approaches 3μm, which means that the focusing position Z1 is 3μm away from the best focusing position of the groove 201 of the test object 200.

[0081] Please continue to refer to Figure 7 , Figure 7 which is a conversion comparison schematic diagram showing the conversion of the wavelength of the interference spectrum to the defocus distance. As Figure 2 , Figure 4 and Figure 7 shown, when the interference objective lens module 3 focuses on a test object 200 at a focusing position Z2, it will correspondingly generate an interference beam IB. Then, after the spectral light collection module 5 collects the light to generate an interference spectrum, it will also be converted to a defocus distance through the spectral analysis module 6; among them, the intensity corresponding to the focusing position Z2 is concentrated at the position where the defocus distance approaches 10μm, which means that the focusing position Z2 is 10μm away from the best focusing position of the groove 201 of the test object 200.

[0082] From the above description, it can be seen that when the interference objective lens module 3 focuses at different positions, the corresponding defocus distances can be generated through the spectral light collection module 5 and the spectral analysis module 6.

[0083] Please continue to refer to Figure 8 , Figure 8 which is a schematic diagram showing the comparison between the scanning position and the focusing position measured by the fast focusing method of the white light interferometer provided by the preferred embodiment of the present invention. As Figure 2 , Figure 4 and Figure 8 shown, a fast focusing method for a white light interferometer includes the following steps S110 to S170.

[0084] First, in step S110, the interference objective lens module 3 is focused on a first position A within the spectral interference technology working range SR; wherein, the spectral interference technology working range SR in this embodiment is, for example, 200 μm, which means that the focusing position of the interference objective lens module 3 can move 200 μm from the starting point (0 μm) along the scanning direction D1 to reach the end point, and the first position A is, for example, at a scanning position of 10 μm, which is a distance of 10 μm moved from the starting point along the scanning direction D1. In addition, the focusing of the interference objective lens module 3 is mainly achieved by the telescopic movement of the lens barrel 31 along the scanning direction D1, or by controlling the movement of the convex lens 32 within the lens barrel 31 in the scanning direction D1, and the spectral interference technology working range SR is the movement limit of the lens barrel 31 or the convex lens 32 in the scanning direction D1.

[0085] In step S120, a detection beam WB is projected from the interference objective lens module 3 towards the object to be measured 200, so that the detection beam WB reflects a first reflected beam (not shown in the figure) from the object to be measured 200. After the interference objective lens module 3 receives the first reflected beam and forms an interference to generate a first interference beam (not shown in the figure, equivalent to the interference beam IB generated when the interference objective lens module 3 is focused on the first position A), the spectral light receiving module 5 receives the first interference beam and analyzes a first interference spectrum; wherein, the detection beam WB projected from the interference objective lens module 3 towards the object to be measured 200 is provided by the white light source 2 in this embodiment, and after being magnified by the convex lenses 12 and 13, it is split by the beam splitter 14 and then focused and projected onto the object to be measured 200 through the interference objective lens module 3. The first beam reflected from the object to be measured 200 refers to the beam reflected from the object to be measured 200 to between the beam splitters 33. Actually, when the reflected beam passes through the beam splitter 33, the reflected beam will be mixed with the beam reflected from the reference mirror 34 to form a first interference beam, and then the first interference beam will pass through the beam splitters 14 and 51 in sequence, and finally be collected by the convex lens 52 to the fiber optic cable light receiver 53 to form a first interference spectrum.

[0086] Next, in step S130, the interference objective lens module 3 is moved along the scanning direction D1 by a scanning movement amount to a second position B1 within the working range SR of the spectral interference technology, and the scanning movement amount is greater than or equal to an analysis misalignment distance interval AR of the spectral analysis module 6; wherein, the analysis misalignment distance interval AR is the sensitivity during the analysis of the spectral analysis module 6. When the scanning movement amount of the interference objective lens module 3 is lower than the analysis misalignment distance interval, the spectral analysis module 6 naturally cannot perform analysis. For example, when the analysis misalignment distance interval of the spectral analysis module 6 is 1 μm, the scanning movement amount needs to be 1 μm or more for calculation.

[0087] In step S140, a detection beam WB is projected towards the object to be measured via the interference objective lens module 3, so that the detection beam WB reflects a second reflected beam (not shown in the figure) from the object to be measured 200. After the interference objective lens module receives the second reflected beam and forms interference to generate a second interference beam (not shown in the figure, equivalent to the interference beam IB generated when the interference objective lens module 3 is focused at the second position B1), the spectral light receiving module 5 receives the second interference beam and analyzes it to obtain a second interference spectrum; wherein, the second beam reflected from the object to be measured 200 refers to the beam reflected from the object to be measured 200 to between the beam splitters 33. Actually, when the reflected beam passes through the beam splitter 33, the reflected beam will be mixed with the beam reflected from the reference mirror 34 to form a second interference beam, and then the second interference beam will sequentially pass through the beam splitters 14 and 51, and finally be collected by the convex lens 52 to the fiber optic cable light receiver 53 for light collection to form a second interference spectrum.

[0088] In step S150, the spectral analysis module 6 is used to analyze the first interference spectrum and the second interference spectrum, thereby respectively generating a first defocus distance a and a second defocus distance b1; in this embodiment, the first defocus distance a is 90 μm, and the second defocus distance b1 is 80 μm.

[0089] In step S160, when the first defocus distance (taking the first defocus distance a of 90 μm as an example) is greater than or equal to the second defocus distance (taking the second defocus distance b1 of 80 μm as an example), the first position A is increased by the first defocus distance a along the scanning direction D1 (that is, moving from the starting point to the scanning position 10 μm and then moving the first defocus distance a of 90 μm to reach the scanning position at 100 μm) to serve as an optimal focusing position BF.

[0090] Please continue to refer to Figure 9 , Figure 9 is a comparison schematic diagram showing the difference between the first scanning position and the second scanning position measured by the fast focusing method of the white light interferometer provided by the preferred embodiment of the present invention compared to the analysis misalignment distance interval of the spectral analysis module. As Figure 2 , Figure 4 ,Figure 5 , Figure 8 As shown in Figure 9 , in actual application, when the best focus position BF is, for example, 100 μm, the interference spectrum near the best focus position BF only has low-frequency oscillations as shown in the intensity vs. defocus distance diagram, which leads to errors in the calculated values. That is, the analysis misalignment distance interval of the above spectral analysis module 6 (for example, 10 μm in this embodiment). Therefore, the difference c between the first defocus distance a and the second defocus distance b1 needs to be greater than or equal to the analysis misalignment distance interval. Since the first defocus distance a in this embodiment is 90 μm, the second defocus distance b1 is 80 μm, and the difference c between the two is 10 μm, it is possible to effectively avoid errors in the calculated values. Figure 5

[0091] Figure 8 Please continue to refer to the above Figure 8 . Based on the fact that in step S110, the interference objective lens module 3 is focused on the first position A within the working range SR of the spectral interference technique, in step S130, in addition to being able to focus the interference objective lens module 3 along the scanning direction D1 on the second position B1 according to the lowest scanning movement amount of 10 μm (i.e., greater than or equal to the analysis misalignment distance interval of 10 μm), it can also be focused on the second position B2 or B3.

[0092] As mentioned above, when focused on the second position B2 (scanning position is 150 μm), even without knowing the best focus position BF, since the second interference spectrum corresponding to the second position B2 can be known to have a second defocus distance b2 of 50 μm after being analyzed by the spectral analysis module 6. According to the above step S160, the first defocus distance a (90 μm) is greater than the second defocus distance b2 (50 μm). The scanning position (100 μm) reached by increasing the first defocus distance a (90 μm) along the scanning direction D1 from the first position A is still taken as a best focus position BF.

[0093] Finally, continue with step S170. Step S170 is to adjust the focus position of the interference objective lens module 3 to the best focus position BF. Among them, when in step S160, the first defocus distance a at the first position A and the second defocus distance b1 at the second position B1 are compared and judged to analyze the best focus position BF, since the scanning position of the second position B1 corresponds to 20 μm, in fact, the focal length of the interference objective lens module 3 will be moved 80 μm along the scanning direction D1 from the second position B1 and focused on the scanning position of 100 μm. Relatively, when in step S160, the first defocus distance a at the first position A and the second defocus distance b2 at the second position B2 are compared and judged to analyze the best focus position BF, since the scanning position of the second position B1 corresponds to 20 μm, in fact, the focal length of the interference objective lens module 3 will be moved 50 μm in the reverse direction of the scanning direction D1 from the second position B2 and focused on the scanning position of 100 μm. It can be seen from this that step S160 mainly compares the first defocus distance a with the second defocus distances b1, b2 or b3 first to judge the relative correction direction, and then uses the largest boundary value (when the difference between the first defocus distance minus the second defocus distance is positive, the first defocus distance is the largest boundary value; when the difference between the first defocus distance minus the second defocus distance is negative, the second defocus distance is the largest boundary value) as the basis to calculate the best focus position BF. However, step S170 calculates the actual correction direction and correction amount based on the scanning position of the second position (B1, B2 or B3) compared with the scanning position corresponding to the best focus position BF, so that the focal length of the interference objective lens module 3 can be directly moved to the best focus position BF for focusing.

[0094] Please continue to refer to Figure 10 , Figure 10 which is a schematic diagram showing the comparison between another scanning position and the focus position measured by using the fast focusing method of the white light interferometer provided by the preferred embodiment of the present invention. As Figure 2 , Figure 4 , Figure 8 and Figure 10 shown, in addition to when the first defocus distance a is greater than or equal to the second defocus distances b1, b2 or b3 in the above step S160, the first position A will be increased by the first defocus distance a along the scanning direction D1 as the best focus position BF. When the first defocus distance a1 (70 μm) of the first position A1, the first defocus distance a2 (30 μm) of the first position A2 or the first defocus distance a3 (5 μm) of the first position A3 is less than the second defocus distance b (80 μm) of the second position B (the scanning position is at 180 μm), the position obtained by increasing the second defocus distance b in the opposite direction of the scanning direction D1 from the second position B (the scanning position is at 180 μm), that is, the scanning position of 180 μm minus 80 μm), is used as the best focus position.

[0095] In summary, in the present invention, the focal length of the interference objective lens module is first set to a first position within the working range of the spectral interference technology to obtain a corresponding first interference spectrum. Then, the focal length of the interference objective lens module is moved along the scanning direction and set to a second position within the working range of the spectral interference technology to obtain a corresponding second interference spectrum. Next, the first interference spectrum and the second interference spectrum are analyzed by a spectral analysis module to respectively generate a first defocus distance and a second defocus distance. Furthermore, the best focusing position is calculated by comparing and judging the first defocus distance and the second defocus distance. Finally, the focal length of the interference objective lens module is set to the best focusing position. Therefore, through the fast focusing method of the white light interferometer provided by the present invention, the interference objective lens module only needs to focus on the first position to obtain the first interference spectrum, then focus on the second position to obtain the second interference spectrum, and then directly focus the interference objective lens module on the best focusing position after calculating the best focusing position through analysis and operation. It is very fast and convenient. Compared with the prior art white light interferometer that needs to focus by scanning and can only know the best focusing position through analyzing the scanned image, the present invention is not only faster but also more accurate.

[0096] Through the detailed description of the above preferred specific embodiments, it is hoped that the features and spirit of the present invention can be more clearly described, rather than limiting the scope of the present invention by the above-disclosed preferred specific embodiments. On the contrary, the purpose is to hope to cover various changes and equivalent arrangements within the scope of the patent application of the present invention.

Claims

1. A rapid focusing method for a white light interferometer, characterized in that, Applied to a white light interferometer having a spectral light collection module and implemented with a spectral analysis module, and the white light interferometer has an interference objective lens module and is provided with a spectral interference technology working range, the spectral analysis module has an analysis misalignment distance interval, and the fast focusing method of the white light interferometer includes the following steps: (A) Set the focal length of the interference objective lens module at a first position within the spectral interference technology working range; (B) Project a detection beam towards a measurement object through the interference objective lens module, so that the detection beam reflects a first reflected beam from the measurement object. After the first reflected beam is received by the interference objective lens module to form interference and generate a first interference beam, the spectral light collection module receives the first interference beam and analyzes it to obtain a first interference spectrum; (C) Move the focal length of the interference objective lens module along a scanning direction by a scanning movement amount to a second position within the spectral interference technology working range, and the scanning movement amount is greater than or equal to the analysis misalignment distance interval; (D) Project the detection beam towards the measurement object through the interference objective lens module, so that the detection beam reflects a second reflected beam from the measurement object. After the second reflected beam is received by the interference objective lens module to form interference and generate a second interference beam, the spectral light collection module receives the second interference beam and analyzes it to obtain a second interference spectrum; (E) Use a spectral analysis module to analyze the first interference spectrum and the second interference spectrum, so as to respectively generate a first defocusing distance and a second defocusing distance; (F) When the first defocusing distance is greater than or equal to the second defocusing distance, increase the position of the first defocusing distance along the scanning direction from the first position as an optimal focusing position; when the first defocusing distance is less than the second defocusing distance, increase the position of the second defocusing distance along the direction opposite to the scanning direction from the second position as the optimal focusing position; and (G) Adjust the focal length of the interference objective lens module to the optimal focusing position.

2. The rapid focusing method of the white light interferometer according to claim 1, characterized in that, The interference objective lens module is a Mirau type interference objective lens module, a Michelson type interference objective lens module or a Linnik type interference objective lens module.

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