Three-dimensional on-line detection system for oil abrasive particles

Abstract

The application provides a lubricating oil abrasive particle three-dimensional online detection system, which comprises a light source system, a beam splitter, a sampling system, a phase modulation system and a detection system; the light source system is used for emitting a parallel light beam to the beam splitter; the beam splitter divides the parallel light beam into two identical transmission light beams and reflection light beams; the reflection light beam illuminates the flowing lubricating oil abrasive particles in the sampling system and generates a scattering light beam which returns to the beam splitter; the transmission light beam returns to the beam splitter as a reference light beam through different optical paths under the modulation of the phase modulation system; the reference light beam and the scattering light beam interfere to form an interference light beam which is incident to the detection system to obtain interference spectrum information of the interference light beam; the amplitude and phase information of the cross-correlation term in the interference light intensity expression are extracted from the interference spectrum information to construct a complex function of the interference light beam signal, then the complex function is subjected to Fourier transform, and finally a clear three-dimensional reconstruction image of the lubricating oil abrasive particle is obtained.

Description

Technical Field

[0001] This invention relates to the field of imaging instrument technology, and in particular to a three-dimensional online detection system for lubricating oil abrasive particles. Background Technology

[0002] Aero engines are critical components of aircraft, with complex internal structures. Under high temperature and high load conditions, they are prone to component wear, seriously threatening operational safety. Of major aircraft accidents caused by mechanical reasons, approximately 40% are due to engine failure, with wear-related failures accounting for over 80%. Therefore, detecting the wear condition of aero engines is of great significance for accelerating their development, ensuring service safety, and preventing catastrophic accidents. Lubricating oil in aero engines is used to lubricate, cool, and clean bearings, gears, and other moving parts. When engine wear occurs, abrasive particles generated on the surfaces of components enter the lubricating oil system, resulting in oil containing abrasive particles of different shapes caused by various types of wear. A sudden increase in the abrasive particle generation rate indicates abnormal engine wear; the morphology and composition of the abrasive particles can identify the location of the wear; and the number, shape, and size of the abrasive particles can determine the type and degree of wear. Therefore, detecting the characteristic parameters such as the number, size, and shape of abrasive particles in the lubricating oil can effectively assess the wear condition of aero engine equipment.

[0003] Current abrasive particle detection methods employ optical, electromagnetic, and chemical methods to obtain various indicators of lubricating oil abrasive particles, thereby determining the wear condition of aero engines. Based on the detection method, these can be divided into offline and online detection. Offline detection typically involves collecting oil samples and then analyzing them using methods such as ferrography, scanning electron microscopy, or atomic emission spectroscopy. While this method offers high accuracy, it is resource-intensive and cannot provide timely information on engine wear conditions. Existing online detection methods primarily use detectors based on electromagnetic induction, which are mostly limited to detecting the size and quantity of lubricating oil particles, failing to acquire shape information. Currently, abrasive particle detection technology is increasingly improving in sensitivity and counting reliability, and abrasive particle information is evolving from simple raw signal feature extraction to image analysis and refined feature extraction and classification. Summary of the Invention

[0004] In view of the above problems, the purpose of this invention is to propose a three-dimensional online detection system for lubricating oil abrasive particles. This system utilizes a Michelson interferometer structure to acquire the interference spectra of the sample beam and the reference beam, and performs Fourier transform and other processing to achieve three-dimensional imaging of the abrasive particles. Simultaneously, a phase-shifting micromirror structure is employed to achieve multi-channel static phase modulation, solving the image and parasitic image problems of single-channel interferometric imaging. This system offers advantages such as fast imaging speed, high clarity, good stability, and compact structure, making it suitable for online detection of lubricating oil abrasive particles.

[0005] To achieve the above objectives, the present invention adopts the following specific technical solution:

[0006] This invention provides a three-dimensional online detection system for lubricating oil abrasive particles, including a light source system, a beam splitter, a sampling system, a phase modulation system, and a detection system;

[0007] The light source system is used to emit a parallel beam of light that is incident on the beam splitter;

[0008] The beam splitter divides the parallel beam into two identical transmitted and reflected beams, which are then incident on the phase modulation system and the sampling system, respectively.

[0009] The sampling system includes: a scanning mirror, an objective lens, and an oil abrasive detection area;

[0010] The sampling system is used to collect three-dimensional information of lubricating oil samples on the oil abrasive detection area, which is used to hold lubricating oil samples extracted from aero engines.

[0011] The scanning mirror is set to a rectangle and rotates around the axis of symmetry of its reflecting surface. The center of the scanning mirror coincides with the image-side focal point of the objective lens.

[0012] in,

[0013] After the reflected beam is incident on the sampling system, it is reflected by the scanning mirror and refracted by the objective lens and then converges into the oil abrasive detection area. The reflected beam provides linear illumination to the flowing lubricating oil abrasive particles in the oil abrasive detection area and interacts with the abrasive particles in the lubricating oil sample to generate a scattered beam containing information about the lubricating oil sample, which returns to the beam splitter along the original path.

[0014] The transmitted beam, modulated by the phase modulation system, travels through different optical paths and returns to the beam splitter via the original path as a reference beam.

[0015] The reference beam and the scattered beam interfere at the exit position of the beam splitter, forming an interference beam that is then incident on the detection system to obtain the interference spectrum information of the interference beam;

[0016] The amplitude and phase information of the cross-correlation terms in the interference intensity expression are extracted from the interference spectrum information to construct a complex function of the interference beam signal. Then, a Fourier transform is performed on the complex function to finally obtain a clear three-dimensional reconstructed image of lubricating oil abrasive particles.

[0017] Preferably, the light source system includes: a light source and a collimating lens;

[0018] The light source is a near-infrared broadband light source. The low-coherence light emitted by the light source is incident on the collimating lens, and after being collimated by the collimating lens, it becomes a parallel beam that is incident on the beam splitter.

[0019] Preferably, the beam splitter is placed at a 45° angle to the optical axis, with a beam splitting ratio of 1:1.

[0020] Preferably, the objective lens is a telecentric optical path on the object side.

[0021] Preferably, the lubricating oil sample from the aircraft engine is pumped into the sampling system by a peristaltic pump to reach the oil abrasive detection area. The channel of the oil abrasive detection area is made of a material that is transparent to the imaging wavelength and has a rectangular cross-section.

[0022] Preferably, the phase modulation system includes a focusing mirror and a phase-shifting micromirror;

[0023] The focusing lens adopts an image-side telecentric optical path design;

[0024] The phase-shifting micromirror is fabricated using the MOEMS process and consists of steps with a reflective coating on the surface of each step.

[0025] Preferably, the detection system includes: a dispersive grating, an imaging mirror, and an area array detector;

[0026] The interference beam is dispersed by a dispersion grating and then converged to an array detector by an imaging mirror, resulting in interference spectral information under different phase modulation channels.

[0027] Preferably, the scanning direction of the scanning mirror is perpendicular to the flow direction of the aero-engine lubricating oil sample.

[0028] Preferably, for a beam that has undergone static phase modulation in any phase modulation channel:

[0029] Let the reference beam signal be:

[0030] I R(k) =S R(k) e i2kr

[0031] Among them, S R(k) Let e ​​be the spectral power distribution function of the reference beam. i2kr is the phase, 2r is the optical path length of the reference beam, and k is the wave number;

[0032] Let the scattered beam signal be:

[0033]

[0034] Among them, S S(k，z) Let be the spectral power density function of reflected light from different depth layers of the lubricating oil sample, n be the refractive index of the lubricating oil sample, and r+nz be the optical path length of reflected light at depth z in the lubricating oil sample;

[0035] The interference spectrum signal I(k) generated after the interference of the reference beam and the scattered beam is:

[0036]

[0037] The actual area array detector detects the real part I'(k) of the interference spectrum signal I(k), then the expression for the actual interference spectrum signal I′(k) is:

[0038]

[0039] By performing a Fourier transform on the intermediate term of the actual interference spectral signal I'(k), the depth information of the lubricating oil sample in that channel can be obtained using FFT{I (k)},Right now:

[0040]

[0041] The acquisition of depth information of lubricating oil samples by a single channel is subject to interference from DC terms and cross-correlation terms of reflections from each depth layer. In addition, since the area array detector can only acquire the real part of the interference spectrum signal and cannot acquire the imaginary part, it also leads to conjugate image interference.

[0042] The interference signal I(k) with wavelength λ simplifies to:

[0043]

[0044] in,

[0045] I0 represents the DC term and the self-coherent term;

[0046] A and φ are the amplitude and phase of the interference signal, respectively;

[0047] The real part I′ of the interference signal with wavelength λ obtained on the area array detector is:

[0048]

[0049] Preferably, when the number of steps in the phase-shifting micromirror is n: the spatial arrangement of the steps can generate a phase shift of π / 2 in each phase modulation channel, and the interference spectrum signals of n channels at the test point can be obtained through a single imaging: the amplitude A and phase of the interference signal can be solved. By constructing a complex function of the interference signal and performing a Fourier transform on the complex function of the interference signal, the depth information of the lubricating oil abrasive particles can be obtained.

[0050] Compared with existing technologies, this invention extracts the three-dimensional information of abrasive particles based on the principle of light interference, solving the problem that traditional detection methods are difficult to achieve three-dimensional imaging of abrasive particles. It utilizes a Michelson interference structure to obtain the interference spectra of the sample beam and the reference beam, and performs Fourier transform and other processing to achieve three-dimensional imaging of the abrasive particles. Simultaneously, it employs a phase-shifting micromirror structure to achieve multi-channel static phase modulation, solving the problems of mirror images and parasitic images in single-channel interference imaging. This invention has the advantages of fast imaging speed, high clarity, good stability, and compact structure, making it suitable for online detection of lubricating oil abrasive particles. Attached Figure Description

[0051] Figure 1 This is a schematic diagram of the structure of a three-dimensional online detection system for lubricating oil abrasive particles provided in an embodiment of the present invention.

[0052] Figure 2 This is a schematic diagram of the converging optical path of a phase-shifting micromirror provided according to an embodiment of the present invention.

[0053] Figure 3 This is a schematic diagram of the scanning imaging optical path of the scanning mirror according to an embodiment of the present invention.

[0054] Figure 4 This is a schematic diagram showing the correspondence between different channels of the phase-shifting micromirror and the imaging surface of the oil abrasive detection area according to an embodiment of the present invention.

[0055] Figure 5 This is a schematic diagram of the position of the dispersive grating and the spectral distribution of the area array detector according to an embodiment of the present invention.

[0056] The reference numerals in the accompanying drawings include: broadband light source 1, collimating lens 2, beam splitter 3, scanning mirror 4, objective lens 5, oil abrasive detection area 6, focusing lens 7, phase-shifting micromirror 8, dispersive grating 9, imaging mirror 10, and area array detector 11. Detailed Implementation

[0057] In the following description, embodiments of the invention will be described with reference to the accompanying drawings. In the description below, the same modules are denoted by the same reference numerals. Where the same reference numerals are used, their names and functions are also the same. Therefore, their detailed description will not be repeated.

[0058] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not constitute a limitation thereof.

[0059] Figure 1 The structure of a three-dimensional online detection system for lubricating oil abrasive particles provided according to an embodiment of the present invention is shown.

[0060] like Figure 1 As shown, the three-dimensional online detection system for lubricating oil abrasive particles provided in this embodiment of the invention adopts a Michelson interferometer structure and includes a light source system, a beam splitter 3, a sampling system, a phase modulation system, and a detection system.

[0061] The light source system includes: light source 1 and collimating lens 2; light source 1 is a broadband light source, and near-infrared light source with strong penetration capability of lubricating oil can be selected. The low coherence light emitted is incident on collimating lens 2, and after being collimated by collimating lens 2, it becomes a parallel beam and is incident on beam splitter 3.

[0062] Beam splitter 3 is placed at 45° to the optical axis, with a splitting ratio of 1:1. Beam splitter 3 splits the parallel beam into two identical transmitted and reflected beams, which are then incident on the phase modulation system and the sampling system, respectively.

[0063] The phase modulation system includes a focusing mirror 7 and a phase-shifting micromirror 8.

[0064] Figure 2 The converging optical path of a phase-shifting micromirror provided according to an embodiment of the present invention is shown.

[0065] like Figure 2 As shown, in the three-dimensional online detection system provided by the present invention, in order to ensure that the light path reflected by the phase-shifting micromirror 8 can return along the incident path, the focusing mirror 7 adopts an image-side telecentric optical path design.

[0066] The phase-shifting micromirror 8 can be fabricated using the MOEMS process and consists of several steps, each coated with a reflective film. Each step corresponds to a phase modulation channel. Static phase modulation of the beam is achieved through the different spatial positions of each step, eliminating the need for additional movable structures and ensuring the system's imaging efficiency and stability.

[0067] In one embodiment of the present invention, the number of steps is 5, that is, 5 steps correspond to 5 phase modulation channels.

[0068] The sampling system includes: a scanning mirror 4, an objective lens 5, and an oil abrasive detection area 6.

[0069] Figure 3 The scanning imaging optical path of the scanning mirror provided according to an embodiment of the present invention is shown.

[0070] like Figure 3 As shown, the sampling system is used to collect three-dimensional information of the lubricating oil sample on the oil abrasive detection area 6, which is used to hold the lubricating oil sample extracted from the aero-engine.

[0071] To acquire an OCT image of the entire oil wear particle detection area 6, the light beam needs to be oscillated. The scanning mirror 4 is set as a rectangle and rotates around its axis of symmetry, with the center of the rectangle coinciding with the image-side focal point of the objective lens 5. The scanning direction is perpendicular to the flow direction of the aero-engine lubricating oil. This achieves scanning imaging at different locations within the detection area, where the objective lens 5 is a telecentric optical path on the object side.

[0072] The lubricating oil sample from the aircraft engine is first pumped into the lubricating oil sampling system by a peristaltic pump to reach the oil abrasive detection zone 6. The channel of the oil abrasive detection zone 6 is made of a material that is transparent to the imaging wavelength and has a rectangular cross-section.

[0073] in,

[0074] After the reflected beam is incident on the sampling system, it is reflected by the scanning mirror 4 and refracted by the objective lens 5 before converging into the oil wear particle detection area 6. The lubricating oil of the aero-engine flows into the oil wear particle detection area 6 in the direction of the arrow. The reflected beam provides linear illumination to the lubricating oil wear particles flowing in the oil wear particle detection area 6. After interacting with the wear particles in the lubricating oil, it generates a scattered echo (sample light). The scattered beam carrying the lubricating oil sample information returns to the beam splitter 3 along the original path.

[0075] After the transmitted beam is incident on the phase modulation system, it is refracted by the focusing mirror 7 and converged to the phase shifting micromirror 8. After being reflected by the step surfaces located at different spatial positions on the phase shifting micromirror 8, it returns to the beam splitter 3 as a reference beam (at this time, the reference beam travels through different optical paths under the modulation of the step surfaces at different spatial positions on the phase shifting micromirror 8).

[0076] The reference beam and the scattered beam interfere at the exit position of beam splitter 3, forming an interference beam that is then incident on the detection system.

[0077] The detection system includes: a dispersive grating 9, an imaging mirror 10, and an area array detector 11.

[0078] The interference beam is dispersed by the dispersion grating 9 and then converged to the area array detector 11 by the imaging mirror 10, thus obtaining interference spectral information under different phase modulation channels.

[0079] Figure 4 The correspondence between different channels of the phase-shifting micromirror provided according to an embodiment of the present invention and the imaging surface of the oil abrasive detection area is shown.

[0080] Under the scanning action of the scanning mirror 4, each phase modulation channel images different regions on the object surface (flowing lubricating oil). The correspondence between the different steps on the phase-shifting micromirror 8 and the imaging regions on the object surface is as follows: Figure 4 As shown, when the lubricating oil flows through the corresponding imaging area of ​​a certain channel on the object surface, the tilting mirror quickly scans the object surface once, and the area array detector 11 acquires the interference spectrum of the imaging surface corresponding to each channel. After the lubricating oil flows through five channels, the area array detector 11 can acquire the lubricating oil interference spectrum of the five channels.

[0081] Because the three-dimensional online inspection system provided by this invention uses linear light source illumination, a linear field of view is also formed on the stepped phase-shifting mirror. Each step / channel corresponds to a different position in the lubricating oil inspection area. The scanning mirror repeatedly scans the entire inspection area laterally with the light beam. When the abrasive particles in the lubricating oil flow longitudinally through the corresponding positions of each channel in the inspection area, imaging of five channels with different optical paths can be achieved.

[0082] Figure 5 A diagram showing the position of the dispersive grating and the spectral distribution of the area array detector provided according to an embodiment of the present invention is shown.

[0083] like Figure 5 As shown, the area array detector 11 receives interference information from five channels in the direction parallel to the grating fringes and spectral information from five channels in the direction perpendicular to the grating fringes. The amplitude and phase information of the cross-correlation terms in the interference intensity expression can be extracted from the interference spectrum to construct a complex function of the interference beam signal. Then, Fourier transform is performed on the reconstructed complex function to eliminate parasitic terms and mirror images, resulting in a clear three-dimensional reconstruction image of lubricating oil abrasive particles.

[0084] The above calculation process includes:

[0085] For a beam that has undergone static phase modulation in a phase modulation channel of the three-dimensional detection system provided by this invention, its interference spectrum is obtained after the interference of the reference beam and the scattered beam. Let the reference beam signal be:

[0086] I R(k) =S R(k) e i2kr

[0087] Among them, S R(k) Let e ​​be the spectral power distribution function of the reference beam. i2kr is the phase, 2r is the optical path length of the reference light, and k is the wave number.

[0088] Let the signal of the scattered beam reflected back from the lubricating oil sample be:

[0089]

[0090] Among them, S S(k，z) Let be the spectral power density function of reflected light from different depth layers of the lubricating oil sample, n be the refractive index of the sample, and r+nz be the optical path length of reflected light at depth z in the sample.

[0091] The interference spectrum signal I(k) generated after the reference beam and the scattered beam interfere is:

[0092]

[0093] The actual area array detector detects the real part I′(k) of the interference spectrum signal I(k), and the expression for the actual interference spectrum signal I′(k) is:

[0094]

[0095] The above formula consists of three terms: the first term is the DC component, the second term is the sum of multiple cosine functions, which contains the depth structure information of the lubricating oil sample, and the third term is the mutual interference between different reflective layers of the lubricating oil sample.

[0096] By performing a Fourier transform on the second term of the actual interference spectral signal I′(k), the depth information of the lubricating oil sample in that channel can be obtained using FFT{I (k)},Right now:

[0097]

[0098] The acquisition of depth information of lubricating oil samples by a single channel is subject to interference from DC terms and cross-correlation terms of reflections from each depth layer. In addition, since the area array detector can only acquire the real part of the interference spectrum signal and cannot acquire the imaginary part, it also leads to conjugate image interference.

[0099] The interference signal I(k) with wavelength λ can be simplified as follows:

[0100]

[0101] in,

[0102] I0 represents the DC term and the self-coherent term, while A and φ represent the amplitude and phase of the interference signal. Only by finding these two terms can the complex function of the interference signal be reconstructed, thereby eliminating interference such as mirror images and parasitic images.

[0103] The real part I′ of the interference signal with wavelength λ obtained on the area array detector is:

[0104]

[0105] Through the modulation effect of the phase-shifting micromirror of this invention, taking a five-step scale as an example, the spatial arrangement of the steps can cause each modulation channel to generate a phase shift of π / 2. At this time, the interference spectral signals of the five channels of the test point can be obtained in a single imaging:

[0106]

[0107] The amplitude A and phase of the cross-correlation term in the expression for interference light intensity can be directly obtained from the above equation.

[0108]

[0109]

[0110] The phase-shifting micromirror used in this invention achieves multi-channel static modulation of the beam phase through the spatial arrangement of stepped reflective surfaces, without adding any additional movable structures, thus ensuring the stability of the system. Furthermore, the phase-shifting stepped reflector in this invention can achieve phase modulation of multiple channels simultaneously, significantly improving the imaging efficiency of the system.

[0111] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

[0112] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A three-dimensional online detection system for lubricating oil abrasive particles, characterized in that, This includes a light source system, a beam splitter, a sampling system, a phase modulation system, and a detection system; The light source system is used to emit a parallel beam of light that is incident on the beam splitter; The beam splitter divides the parallel beam into two identical transmitted beams and reflected beams, which are respectively incident on the phase modulation system and the sampling system. The sampling system includes: a scanning mirror, an objective lens, and an oil abrasive detection area; The sampling system is used to collect three-dimensional information of the lubricating oil sample on the oil abrasive detection area, which is used to hold the lubricating oil sample extracted from the aero-engine. The scanning mirror is rectangular and rotates around the axis of symmetry of its reflecting surface. The center of the scanning mirror coincides with the image-side focal point of the objective lens. in, After the reflected beam is incident on the sampling system, it is reflected by the scanning mirror and refracted by the objective lens and then converges into the oil abrasive particle detection area. The reflected beam provides linear illumination to the flowing lubricating oil abrasive particles in the oil abrasive particle detection area and interacts with the abrasive particles in the lubricating oil sample to generate a scattered beam carrying the information of the lubricating oil sample, which returns to the beam splitter along the original path. The transmitted beam, under the modulation of the phase modulation system, travels through different optical paths and returns to the beam splitter via the original path as a reference beam. The reference beam and the scattered beam interfere at the exit position of the beam splitter, forming an interference beam which is then incident on the detection system to obtain the interference spectrum information of the interference beam; The amplitude and phase information of the cross-correlation terms in the interference intensity expression are extracted from the interference spectrum information to construct a complex function of the interference beam signal. Then, a Fourier transform is performed on the complex function to finally obtain a clear three-dimensional reconstructed image of lubricating oil abrasive particles.

2. The three-dimensional online detection system for lubricating oil abrasive particles according to claim 1, characterized in that, The light source system includes: a light source and a collimating lens; The light source is a near-infrared broadband light source. The low-coherence light emitted by the light source is incident on the collimating lens, and after being collimated by the collimating lens, it becomes a parallel beam that is incident on the beam splitter.

3. The three-dimensional online detection system for lubricating oil abrasive particles according to claim 2, characterized in that, The beam splitter is placed at a 45° angle to the optical axis, with a beam splitting ratio of 1:

1.

4. The three-dimensional online detection system for lubricating oil abrasive particles according to claim 3, characterized in that, The objective lens is an object-side telecentric optical path.

5. The three-dimensional online detection system for lubricating oil abrasive particles according to claim 4, characterized in that, The lubricating oil sample from the aero-engine is pumped into the sampling system by a peristaltic pump to reach the oil abrasive detection area. The channel of the oil abrasive detection area is made of a material that is transparent to the imaging wavelength and has a rectangular cross-section.

6. The three-dimensional online detection system for lubricating oil abrasive particles according to claim 5, characterized in that, The phase modulation system includes a focusing mirror and a phase-shifting micromirror; The focusing lens adopts an image-side telecentric optical path design; The phase-shifting micromirror is fabricated using the MOEMS process and consists of steps, the surface of which is coated with a reflective film.

7. The three-dimensional online detection system for lubricating oil abrasive particles according to claim 6, characterized in that, The detection system includes: a dispersive grating, an imaging mirror, and an area array detector; The interference beam is dispersed by the dispersion grating and then converged to the area array detector by the imaging mirror, resulting in interference spectral information under different phase modulation channels.

8. The three-dimensional online detection system for lubricating oil abrasive particles according to claim 7, characterized in that, The scanning direction of the scanning mirror is perpendicular to the flow direction of the aero-engine lubricating oil sample.

9. The three-dimensional online detection system for lubricating oil abrasive particles according to claim 8, characterized in that, For any phase-modulated beam in any phase-modulated channel: Let the reference beam signal be: I R(k) =S R(k) yes i2kr Among them, S R(k) Let e ​​be the spectral power distribution function of the reference beam. i2kr 2r is the phase, 2r is the optical path length of the reference beam, and k is the wave number; Let the signal of the scattered beam be: Among them, S S(k，z) Let be the spectral power density function of the reflected light from different depth layers of the lubricating oil sample, n be the refractive index of the lubricating oil sample, and r+nz be the optical path length of the reflected light at depth z in the lubricating oil sample. The interference spectrum signal I(k) generated after the interference of the reference beam and the scattered beam is: The actual area array detector detects the real part I′(k) of the interference spectrum signal I(k), and the expression for the actual interference spectrum signal I′(k) is: By performing a Fourier transform on the intermediate term in the actual interference spectral signal I′(k), the depth information of the lubricating oil sample in that channel can be obtained using FFT{I (k) },Right now: The acquisition of depth information of lubricating oil samples by a single channel is subject to interference from DC terms and cross-correlation terms of reflections from each depth layer. In addition, since the area array detector can only acquire the real part of the interference spectrum signal and cannot acquire the imaginary part, it also leads to conjugate image interference. The interference signal I(k) with wavelength λ simplifies to: in, I0 represents the DC term and the self-coherent term; A and φ are the amplitude and phase of the interference signal, respectively; The signal obtained on the array detector is the real part I′ of the interference signal with wavelength λ.

10. The three-dimensional online detection system for lubricating oil abrasive particles according to claim 9, characterized in that, When the number of steps in the phase-shifting micromirror is n: the spatial arrangement of the steps allows each phase modulation channel to generate a phase shift of π / 2. Interference spectral signals from n channels at the test point are obtained through a single imaging operation. The amplitude A and phase of the interference signal are then calculated. A complex function of the interference signal is constructed, and a Fourier transform is performed on the complex function of the interference signal to obtain the depth information of the lubricating oil abrasive particles.

Images