Common-path probe for measuring micro-hole and manufacturing method of common-path probe

Abstract

The invention discloses a common-path probe for measuring a micro hole and a manufacturing method, and the probe comprises a transversely extending single-mode optical fiber, a glass sleeve sleeving the right part of the single-mode optical fiber, a transversely extending cylindrical GRIN lens disposed at the right ends of the single-mode optical fiber and the glass sleeve, and a fixed sheath disposed on the glass sleeve and provided with openings at the left end and the right end. The movable sheath sleeves the right part of the fixed sheath; the right end of the movable sheath is closed, a reflecting prism is arranged in the movable sheath, the working face of the reflecting prism is aligned with a light outlet formed in the right portion of the movable sheath, the movable sheath can slide left and right relative to the fixed sheath, and a sealing ring is arranged on the inner circumferential face of the left portion of the movable sheath. The method has the characteristic of being capable of detecting the internal morphology of the micro-hole with the diameter of 1-5 mm.

Description

Technical Field

[0001] The present invention relates to the field of precision detection technology, and particularly relates to a common-path probe for measuring micro-holes and a manufacturing method thereof. Background Art

[0002] In high-precision equipment and systems in the fields of aerospace, automotive, national defense, medicine, etc., micro-hole structures with high machining precision are widespread. In many cases, the inner surface topography thereof will have a great impact on the performance of the system. Accurately and stably measuring the inner surface of the micro-hole can effectively judge whether the machining precision of the parts meets the standard, and is also the basis for improving the machining precision.

[0003] Existing contact or non-contact high-precision surface profilers have insufficient measurement capabilities for the inner surface of micro-holes. Due to the limitations of physical size and optical focal length, the probes of conventional low-coherence interference systems cannot penetrate into the micro-holes, resulting in the inability to measure micro-holes.

[0004] In addition, due to the limitations of the optical measurement principle itself, the measurement effect is affected by the light collection effect. When the inclination angle of the measured object surface is too large, the intensity of the light beam reflected back to the probe is too low, resulting in inability to process; when the height difference between the protruding surface and the concave surface of the measured object surface exceeds the designed working distance of the probe, the surface outside the working distance of the probe cannot be measured. Summary of the Invention

[0005] The invention purpose of the present invention is to overcome the deficiencies of the prior art, and provides a common-path probe for measuring micro-holes and a manufacturing method thereof.

[0006] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0007] A common-path probe for measuring micro-holes includes a single-mode optical fiber extending horizontally, a glass sleeve sleeved on the right part of the single-mode optical fiber, a horizontally extending cylindrical GRIN lens arranged at the right ends of the single-mode optical fiber and the glass sleeve, a fixed sheath with openings at both left and right ends arranged on the glass sleeve, and a movable sheath sleeved on the right part of the fixed sheath; the right end of the movable sheath is closed, a reflecting prism is arranged inside the movable sheath, the working surface of the reflecting prism is aligned with a light outlet arranged at the right part of the movable sheath, the movable sheath can slide left and right relative to the fixed sheath, and a sealing ring is arranged on the inner peripheral surface of the left part of the movable sheath; the movable sheath is used to drive the reflecting prism to move left and right so as to adjust the distance between the focus of the common-path probe and the axis of the common-path probe, the left part of the fixed sheath is a clamping section for cooperating with a matching fixture, the right part of the movable sheath is a working section for penetrating into the micro-hole for measurement, and the outer diameter of the working section is 0.8 mm - 1.0 mm.

[0008] The operating wavelengths of the single-mode optical fiber, GRIN lens, and reflection prism include the light source wavelength. The light beam emitted from the single-mode optical fiber of the present invention is expanded by passing through a glass sleeve, and then the light beam is focused by the GRIN lens, focusing the light beam at a point on the extension line of the probe axis. After the light beam focused by the GRIN lens is reflected by the reflection prism, the light beam exits from the light outlet, perpendicular to the axis of the probe and focused at the focal point. The light beam irradiates the surface of the measured micro-hole within the working distance range, and the light beam reflected from the surface of the measured micro-hole passes through the reflection of the reflection prism and the transmission of the GRIN lens in sequence, returning to the single-mode optical fiber to form the optical path of the measurement arm.

[0009] Preferably, there is no coating layer on the outer peripheral surface of the single-mode optical fiber located inside the glass sleeve, and the outer diameter of the single-mode optical fiber is 0.25 mm; a 1° facet is provided at the connection between the single-mode optical fiber and the GRIN lens.

[0010] The present invention provides a 1° facet at the connection between the single-mode optical fiber and the GRIN lens. Through the 1° facet, a reflected optical path is formed, and this optical path is used as the reference arm optical path of the low-coherence interference system, simplifying the optical path system and providing the stability of the reference arm optical path. The signal of the reference arm optical path is attenuated by the 1° facet to avoid the signal of the reference arm optical path being too strong.

[0011] Traditional low-coherence interference systems need to build the reference arm optical path and the measurement arm optical path separately. The present invention embeds the reference arm optical path into the co-path probe by means of a common path, constructing a reference arm reflected optical path inside the co-path probe, greatly reducing the space occupied by the probe and improving the structural compactness of the probe.

[0012] Preferably, the diameters of the glass sleeve and the GRIN lens are both 0.4 mm - 0.6 mm, the length of the glass sleeve is 10 mm - 15 mm, and the length of the GRIN lens is 4 mm - 8 mm.

[0013] Preferably, the reflection angle of the reflection prism is 45°, 90°, or 135°.

[0014] When measuring micro-holes of different specifications, the measurement can be carried out by replacing the reflection prism with different reflection angles, which can not only achieve the side view of the probe light beam but also meet the requirements of the surface angles of different micro-holes to be measured. When the surface of the micro-hole to be measured has a certain inclination angle, resulting in the probe with a reflection angle of 90° being unable to receive light, a probe with other reflection angles can be selected to meet the measurement requirements.

[0015] Preferably, the edge length of the working surface of the reflection prism corresponding to the GRIN lens is 0.4 mm - 0.6 mm, and the diameter of the cross-section of the GRIN lens is 0.4 mm - 0.6 mm.

[0016] Preferably, both the fixed sheath and the movable sheath are made of PET material.

[0017] A manufacturing method of a common-path probe for measuring micro-holes, comprising the following steps:

[0018] S1. Remove the coating layer on the right part of the single-mode optical fiber, and apply an adhesive on the right part of the single-mode optical fiber.

[0019] S2. Insert the right part of the single-mode optical fiber into the glass sleeve, align the right ends of the single-mode optical fiber and the glass sleeve, and the adhesive bonds the single-mode optical fiber and the glass sleeve.

[0020] S3. Grind the right ends of the single-mode optical fiber and the glass sleeve into 1° facets.

[0021] S4. Grind the left end of the GRIN lens into 1° facet, and use an adhesive to bond the left end of the GRIN lens to the right ends of the single-mode optical fiber and the glass sleeve. After bonding, align the axes of the GRIN lens and the single-mode optical fiber.

[0022] S5. Insert the connected single-mode optical fiber, glass sleeve and GRIN lens into the fixed sheath, so that the right part of the GRIN lens extends beyond the right end of the fixed sheath.

[0023] S6. Fix the reflection prism inside the movable sheath, put the movable sheath on the fixed sheath, align the working surface of the reflection prism with the GRIN lens and the light outlet, and the reflection prism is used to reflect the light beam.

[0024] Therefore, the present invention has the following beneficial effects:

[0025] The outer diameter of the working section does not exceed 1 mm, which is much smaller than the size of the low-coherence interferometer probe, and can meet the requirement of detecting the internal morphology of micro-holes with a diameter of 1 mm to 5 mm;

[0026] Integrate the reference arm optical path into the common-path probe by using the common-path optical path, and improve the structural compactness of the common-path probe on the premise of meeting the optical measurement requirements;

[0027] The reflection prism reflects the emitted light beam out of the light outlet, avoiding the influence of the sheath on the emission optical path;

[0028] The reflection prism reflects the reflected light from the surface of the micro-hole entering from the light outlet, avoiding the attenuation of the reflected signal light by the sheath or the glass dust-proof window;

[0029] Multiple reflection prisms with different reflection angles can meet the requirements of the surface inclination angles of different specifications of the measured micro-holes;

[0030] The movable sheath can move axially relative to the fixed sheath. Although the focal length of the GRIN lens is fixed, by cooperating with the movable reflecting prism, the adjustment of the distance between the probe focus and the probe axis can be achieved;

[0031] The structure is simple, safe and reliable, and easy to use. Description of the Drawings

[0032] Figure 1 It is a cross-sectional view of a common-path probe structure with a reflection angle of 45° of the present invention;

[0033] Figure 2 It is a cross-sectional view of a common-path probe structure with a reflection angle of 90° of the present invention;

[0034] Figure 3 It is a cross-sectional view of a common-path probe structure with a reflection angle of 135° of the present invention;

[0035] Figure 4 It is a schematic diagram of a partial enlarged optical path of the present invention;

[0036] Figure 5 It is a schematic diagram of an optical path of a reflecting prism of the present invention. Detailed Embodiments

[0037] The present invention will be further described below in conjunction with the drawings and specific embodiments.

[0038] As Figures 1 - 3 The embodiment shown is a common-path probe for measuring micro-holes, including a single-mode optical fiber 1 extending horizontally, a glass sleeve 2 sleeved on the right part of the single-mode optical fiber, a horizontally extending cylindrical GRIN lens 3 provided at the right ends of the single-mode optical fiber and the glass sleeve, a fixed sheath 5 with openings at both left and right ends provided on the glass sleeve, and a movable sheath 6 sleeved on the right part of the fixed sheath; the right end of the movable sheath is closed, a reflecting prism 4 is provided inside the movable sheath, the working surface of the reflecting prism is aligned with the light outlet provided on the right part of the movable sheath, the movable sheath can slide left and right relative to the fixed sheath, and a sealing ring 7 is provided on the inner peripheral surface of the left part of the movable sheath; the movable sheath is used to drive the reflecting prism to move left and right so as to adjust the distance between the focus of the common-path probe and the axis of the common-path probe, the left part of the fixed sheath is a clamping section for cooperating with a matching fixture, the right part of the movable sheath is a working section for probing into the inside of the micro-hole for measurement, and the outer diameter of the working section is 0.9 mm. The outer diameter of the thickest part of the left part of the movable sheath is 5.0 mm.

[0039] There is no coating on the outer peripheral surface of the single-mode optical fiber located inside the glass sleeve, and the outer diameter of the single-mode optical fiber is 0.25 mm; a 1° facet is provided at the connection between the single-mode optical fiber and the GRIN lens.

[0040] The diameters of the glass sleeve and the GRIN lens are both 0.5 mm. The length of the glass sleeve is 13 mm, and the length of the GRIN lens is 6 mm. The edge length of the working surface of the reflection prism corresponding to the GRIN lens is 0.5 mm, and the diameter of the cross-section of the GRIN lens is 0.5 mm.

[0041] As Figures 1 - 3 shown, the reflection angles of the reflection prism are 45°, 90° and 135° respectively. Both the fixed sheath and the movable sheath are made of PET material.

[0042] A manufacturing method of a common-path probe for measuring micro-holes, comprising the following steps:

[0043] S1, Remove the coating layer on the right part of the single-mode optical fiber, and apply an adhesive on the right part of the single-mode optical fiber;

[0044] S2, Insert the right part of the single-mode optical fiber into the glass sleeve, align the right ends of the single-mode optical fiber and the glass sleeve, and the adhesive bonds the single-mode optical fiber and the glass sleeve;

[0045] S3, Grind the right ends of the single-mode optical fiber and the glass sleeve into 1° facets;

[0046] S4, Grind the left end of the GRIN lens into a 1° facet, and use an adhesive to bond the left end of the GRIN lens to the right ends of the single-mode optical fiber and the glass sleeve. After bonding, align the axes of the GRIN lens and the single-mode optical fiber;

[0047] S5, Insert the connected single-mode optical fiber, glass sleeve and GRIN lens into the fixed sheath, so that the right part of the GRIN lens extends out of the right end of the fixed sheath;

[0048] S6, Fix the reflection prism inside the movable sheath, put the movable sheath on the fixed sheath, align the working surface of the reflection prism with the GRIN lens and the light outlet, and the reflection prism is used to realize the reflection of the light beam.

[0049] Use the common-path probe of this embodiment to measure micro-holes:

[0050] The interferometer is connected to the left end of the single-mode optical fiber, insert the working section into the micro-hole, the interferometer emits a light beam to the single-mode optical fiber, the light beam is expanded by the glass sleeve, and at the 1° facet as Figure 4 shown, a reflected light path is formed, and this light path is the reference arm light path;

[0051] At the same time, as Figure 4 、 Figure 5As shown, the light beam continues to move rightward through the GRIN lens, which focuses the light beam at a point on the extension of the probe axis. After being focused by the GRIN lens, the light beam is reflected by the reflection prism and then exits from the light output port. The light beam is perpendicular to the axis of the probe and focused at the focal point, irradiating on the surface of the micro-hole to be measured. The light beam reflected from the surface of the micro-hole to be measured passes through the reflection of the reflection prism and the transmission of the GRIN lens in sequence, and returns to the single-mode optical fiber to form the optical path of the measurement arm; Figure 5 In the formula, z is the working distance of the common-path probe in this embodiment, and s is the focal point of the common-path probe in this embodiment. During measurement, only when the surface of the micro-hole to be measured is within the working distance range can it be effectively measured.

[0052] The reference arm optical path and the measurement arm optical path interfere. For a component of a certain optical frequency v of the light source, the signal output by the interferometer can be expressed as:

[0053]

[0054] In the formula: v is the optical frequency, is the interference phase, A(v) is the DC component of the signal, and B(v) is the interference contrast. The frequency-domain white-light interference channel spectrum is periodic, that is, the spectral density is modulated by the cosine function, and the average fringe interval of its interference spectrum is determined by the arm length difference (or cavity length) of the interferometer. Therefore, after performing Fourier transform on the channel spectrum, the main frequency in its amplitude-frequency characteristic corresponds to the average fringe interval of the interference spectrum, thereby measuring the optical path difference of the interferometer.

[0055] Regarding the channel spectrum output by the frequency-domain white-light interferometer as a cosine curve that changes periodically with the optical frequency v, the above formula can be transformed into:

[0056]

[0057] Let the frequency f0 = 2L / c, then the above formula can be changed to:

[0058] S(v) = A(v) + B(v)cos(2πf0v + φ0)

[0059] Performing Fourier transform on the above formula, we can obtain:

[0060] F{S(v)} = F{A(v)} + F{B(v)} * F{cos(2πf0v + φ0}

[0061] In the formula, F{} represents performing Fourier transform on the function, and * represents convolution operation. According to the properties of Fourier transform, from the following formula, we can obtain:

[0062]

[0063] Wherein, G(f) is the Fourier transform of B(v). According to the principle of wide-spectrum light interference, it is the light source density of the wide-spectrum light source; δ(f) is the impulse function. It can be seen from the above formula that the amplitude-frequency curve of F{S(v)} has three peaks, and the peak positions correspond to zero frequency and ±f0. According to the definition of the frequency f0 in the amplitude-frequency curve, the absolute optical path difference L can be obtained as follows:

[0064]

[0065] Through the above calculation, the optical signal can be converted into the absolute optical path difference of the measurement point, and finally the point cloud data of the surface of the measured micro-hole can be obtained. The inner diameter value of the micro-hole can be obtained by fitting and calculating the data.

[0066] Taking the inner diameter measurement of a measuring ring gauge (which is a kind of micro-hole) as an example, the results of the inner diameter measurement are shown in Table 1:

[0067] Table 1 Test results of the inner diameter of the ring gauge

[0068]

[0069] It can be seen from Table 1 that the average value of the measurement results of the 0.992 mm ring gauge is 0.993 mm, the indication error is 0.001 mm, and the repeatability is 2.16 μm; the average value of the measurement results of the 1.002 mm ring gauge is 1.003 mm, the indication error is 0.001 mm, and the repeatability is 3.06 μm.

[0070] Taking the depth-diameter ratio of the measuring ring gauge as an example, when measuring the inner surface, the measurable working depth is also an important index. In this test, two ring gauges were used for the test. The metrological dimension of the first ring gauge is 0.992 mm, and the metrological dimension of the second ring gauge is 0.993 mm. The working surface thickness of both ring gauges is greater than 5 mm. The inner diameters of the working surfaces of the two ring gauges at two different heights were measured respectively, and the depth-diameter ratio was obtained by comparing the height difference with the actual inner diameter of the ring gauge. The measurement results are shown in Table 2:

[0071] Table 2 Test results of the depth-diameter ratio

[0072]

[0073] It can be known that the inner diameter values measured at different heights all reflect that this measurement belongs to the working range of the ring gauge. The measurement results of the depth-diameter ratios of the two ring gauges verify that for a ring gauge with an inner diameter of 1 mm, a depth-diameter ratio greater than 4:1 can be achieved in the measurement.

[0074] It can be seen that the measurement accuracy and measurement repeatability of the present invention are relatively high, with good measurement stability, and it has the ability to measure the minimum inner diameter less than 1 mm, which can meet the needs of measuring micro-holes with a certain depth. For a ring gauge with an inner diameter of 1 mm, a depth-diameter ratio greater than 4:1 can be achieved in the measurement.

[0075] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A common-path probe for measuring micro-holes, characterized in that, It includes a laterally extending single-mode optical fiber (1), a glass sleeve (2) sleeved on the right part of the single-mode optical fiber, a laterally extending cylindrical GRIN lens (3) provided at the right ends of the single-mode optical fiber and the glass sleeve, a fixed sheath (5) with openings at both left and right ends provided on the glass sleeve, and a movable sheath (6) sleeved on the right part of the fixed sheath; the right end of the movable sheath is closed, a reflecting prism (4) is provided inside the movable sheath, the working surface of the reflecting prism is aligned with the light outlet provided on the right part of the movable sheath, the movable sheath can slide left and right relative to the fixed sheath, and a sealing ring (7) is provided on the inner peripheral surface of the left part of the movable sheath; the movable sheath is used to drive the reflecting prism to move left and right so as to adjust the distance between the focus of the common-path probe and the axis of the common-path probe, the left part of the fixed sheath is a clamping section for cooperating with a matching fixture, the right part of the movable sheath is a working section for probing into a micro-hole for measurement, and the outer diameter of the working section is 0.8 mm - 1.0 mm.

2. The common-path probe for measuring a micro-hole according to claim 1, characterized in that, There is no coating layer on the outer peripheral surface of the single-mode optical fiber located inside the glass sleeve, and the outer diameter of the single-mode optical fiber is 0.25 mm; a 1° facet is provided at the connection between the single-mode optical fiber and the GRIN lens.

3. The common-path probe for measuring micro-holes according to claim 1, characterized in that, The diameters of the glass sleeve and the GRIN lens are both 0.4 mm - 0.6 mm, the length of the glass sleeve is 10 mm - 15 mm, and the length of the GRIN lens is 4 mm - 8 mm.

4. The common-path probe for measuring micro-holes according to claim 1, characterized in that, The reflection angle of the reflecting prism is 45°, 90° or 135°.

5. The common-path probe for measuring a micro-hole according to claim 1, characterized in that, The edge length of the working surface of the reflecting prism corresponding to the GRIN lens is 0.4 mm - 0.6 mm, and the diameter of the cross-section of the GRIN lens is 0.4 mm - 0.6 mm.

6. The common-path probe for measuring micro-holes according to claim 1 or 2 or 3 or 4 or 5, characterized in that, Both the fixed sheath and the movable sheath are made of PET material.

7. A manufacturing method of the common-path probe for measuring micro-holes according to claim 1, characterized in that, It includes the following steps: S1, Remove the coating layer on the right part of the single-mode optical fiber and apply an adhesive on the right part of the single-mode optical fiber. S2, Insert the right part of the single-mode optical fiber into the glass sleeve so that the right ends of the single-mode optical fiber and the glass sleeve are aligned, and the adhesive bonds the single-mode optical fiber and the glass sleeve. S3, Grind the right ends of the single-mode optical fiber and the glass sleeve into a 1° facet. S4, Grind the left end of the GRIN lens into a 1° facet, and use an adhesive to bond the left end of the GRIN lens to the right ends of the single-mode optical fiber and the glass sleeve. After bonding, make the axes of the GRIN lens and the single-mode optical fiber coincide. S5, Insert the connected single-mode optical fiber, glass sleeve and GRIN lens into the fixed sheath so that the right part of the GRIN lens extends out of the right end of the fixed sheath. S6, Fix the reflecting prism inside the movable sheath, sleeve the movable sheath on the fixed sheath so that the working surface of the reflecting prism is aligned with the GRIN lens and the light outlet, and the reflecting prism is used to realize the reflection of the light beam.

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