High-precision long-travel optical interval measurement device and method based on optical fiber interconnection

Abstract

The present invention provides a high-precision long-travel optical interval measurement device and method based on optical fiber interconnection, including: a light source, a wavelength division multiplexing device, a beam combiner, a sub-aperture device and a detector device; the light beam emitted by the light source passes through the wavelength division multiplexing device and then passes through the first beam splitter to be divided into a first light beam and a second light beam; the first light beam passes through a beam delay line device to generate an optical path difference and then is transmitted to the sub-aperture device through an optical fiber; the sampling rate of the detection space is increased by rotating the optical system to be measured; the reflected light beam generated by the first light beam returns to the original path and is transmitted to a three-terminal circulator; the reflected light beam of the first light beam and the second light beam generate an interference light beam and are incident on the detector to obtain light intensity; the inclination angle and assembly error of the optical system to be measured are calculated according to the light intensity, and the assembly of the optical system to be measured is guided according to the assembly error. The present invention realizes multi-level error separation and precision tracing, and finally realizes highly robust and high-precision detection of the transmission wavefront of a large-aperture lens.

Description

Technical Field

[0001] The present invention relates to the field of optical measurement technology, and in particular to a high-precision and long-travel optical interval measurement device and method based on optical fiber interconnection. Background Art

[0002] Fast focal ratio large-aperture lenses and lens groups are key links in large-field-of-view aberration correction and fine-tuning of laser energy. They play a very important role in frontier exploration of science and technology (large-aperture astronomical telescopes, inertial confinement fusion), high-resolution remote sensing cameras, and lithography exposure systems. However, there are problems such as high cost of aperture standard gauges such as fast focal ratio large-aperture lenses, large basic aberrations, and increased difficulty in designing and processing zero-position detection devices due to the compact optical path. Summary of the invention

[0003] In view of the above problems, the purpose of the present invention is to propose a high-precision, long-stroke optical interval measurement device and method based on fiber optic interconnection; to address the detection problem of large-aperture transmitted wavefront quality (closest to the usage state), a sub-aperture pupil scanning architecture is utilized to combine holographic wavefront sensing with aperture coding to achieve multi-level error separation and precision tracing, and ultimately achieve highly robust and high-precision detection of large-aperture lens transmitted wavefront.

[0004] To achieve the above object, the present invention adopts the following specific technical solutions:

[0005] The present invention provides a high-precision long-travel optical interval measurement device based on optical fiber interconnection, comprising: a light source, a wavelength division multiplexing device, a beam combiner, a sub-aperture device and a detector device;

[0006] The light beam emitted by the light source is transmitted to the wavelength division multiplexing device through the optical fiber, and the wavelength division multiplexing device is used to form a detection optical path with different bandwidths. Each wavelength division multiplexing device is connected to the detector device respectively, and the detector device includes a first beam splitter, a beam delay line device, a three-terminal circulator, a detector and a second beam splitter;

[0007] The light beam emitted by the light source passes through the wavelength division multiplexing device and then passes through the first beam splitter to be divided into a first light beam and a second light beam;

[0008] The first light beam generates an optical path difference through a beam delay line device, is transmitted to a beam combiner through an optical fiber for beam combining, and then enters the sub-aperture devices respectively; the sub-aperture devices are distributed on the surface of one side of the optical system to be measured; the sampling rate of the detection space is improved by rotating the optical system to be measured using a rotational time-division multiplexing method;

[0009] The first light beam is emitted through the sub-aperture device and then illuminates the optical system to be measured and the large-aperture lens inside it. The generated reflected light beam returns along the original path and is transmitted to the three-end circulator through the second beam splitter.

[0010] The second light beam is emitted from the first beam splitter and then transmitted to the three-terminal circulator through the optical fiber;

[0011] The reflected beam of the first light beam and the second light beam generate an interference beam inside the three-end circulator and then are incident on the detector to obtain the light intensity; the inclination angle and assembly error of the optical system to be measured are calculated according to the light intensity of the interference beam, and the assembly of the optical system to be measured is guided according to the assembly error.

[0012] Preferably, the light source is a swept laser.

[0013] Preferably, the beam delay line device consists of a corner reflector and a large field of view coupler.

[0014] Preferably, when the sub-aperture devices are arranged in a cross shape, the rotation angle of the optical system to be measured is 90°.

[0015] Preferably, when the sub-aperture devices are arranged in an equilateral triangle, the rotation angle of the optical system to be measured is 120°.

[0016] The present invention also provides a high-precision long-travel optical interval measurement method based on optical fiber interconnection, comprising the following steps:

[0017] S1, by controlling the wavelength division multiplexing device and the corner reflector respectively to change the wavelength λ of the i-th first light beam ij and optical path difference Δδ ik ;

[0018] S2, the light intensity I of the interference beam of the i-th first light beam and the second light beam received by the detector i The following equation is obtained:

[0019]

[0020] in,

[0021] E i1 and E i2 The intensity of the i-th interference beam is I i The amount of

[0022] δ i is the original optical path of the i-th interference beam;

[0023] δ i0 is the optical path of the i-th interference beam when the additional delay intensity is 0;

[0024] Δλ is the current wavelength λ ij With the previous wavelength λ ij-1 The difference between ij -λ ij-1 ;

[0025] i = 1, 2, 3, ... n;

[0026] j = 1, 2, 3, ... n;

[0027] k = 1, 2, 3, ... n;

[0028] Then we get at least four nonlinear equations:

[0029]

[0030] Perform Fourier transform on the above equations to transform the nonlinear equations into multivariate linear equations and then solve them to obtain E i1 , E i2 , δ i , δ i0 ;

[0031] S3, after solving the above equations, the characteristic frequency (δ i -δ i0 ), according to the characteristic frequency (δ i -δ i0 ) The inclination angle and assembly error of the optical system to be tested are calculated by the spherometer principle, and the assembly error is used to guide the adjustment of the optical system to be tested.

[0032] Compared with the existing technology, the present invention uses scanning pupil (to improve the detection span) and curvature wavefront sensing (to improve the dynamic range and stability) to obtain the transmission wavefront of a large-aperture lens group, and uses aperture coding to reduce the coupling between the heterogeneous errors of the system. A new system for on-site detection of the transmission system is established with large information flux and error decoupling separation, and the transmission wavefront of the transmission system and the parallel high-throughput near-field measurement of parameters such as focal length and optical surface spacing are realized. The shortcomings of the transmission wavefront detection method in the prior art, such as the difficulty in designing and processing high-precision compensation mirrors and reflectors, the high requirements for the stability of the detection environment, and the inability to realize flexible and flexible processing are overcome. By achieving a transmission wavefront detection accuracy of better than 1 microradian on a span of 300mm, a focal length test accuracy of better than 200 microns, and an optical surface spacing measurement of better than 50 microns, the bottleneck of processing and detection technology of large-aperture transmission optical systems is broken through, which is of great significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic structural diagram of a high-precision and long-travel optical interval measuring device based on optical fiber interconnection provided according to an embodiment of the present invention.

[0034] Figure 2 It is a flow chart of a high-precision and long-travel optical interval measurement method based on optical fiber interconnection provided according to an embodiment of the present invention.

[0035] The reference numerals therein include: light source 1, wavelength division multiplexing device 2, combiner 3, sub-aperture device 4, optical system to be measured 5, detector device 6, first beam splitter 61, beam delay line device 62, three-end circulator 63, detector 64 and second beam splitter 65. DETAILED DESCRIPTION

[0036] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, the same modules are represented by the same reference numerals. In the case of the same reference numerals, their names and functions are also the same. Therefore, the detailed description thereof will not be repeated.

[0037] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation of the present invention.

[0038] Figure 1 A high-precision, long-travel optical interval measuring device based on optical fiber interconnection provided according to an embodiment of the present invention is shown.

[0039] like Figure 1 As shown, the high-precision long-travel optical interval measurement device based on optical fiber interconnection provided in an embodiment of the present invention includes: a light source 1, a wavelength division multiplexing device 2, a combiner 3, a sub-aperture device 4, an optical system to be measured 5 and a detector device 6.

[0040] The light beam emitted by the light source 1 is transmitted to multiple wavelength division multiplexing devices 2 through optical fibers. The wavelength division multiplexing devices 2 are used to form multiple detection optical paths with different bandwidths, and optical switches are used for switching to achieve high-precision, large-range and highly robust measurements under different wavelength encoding effects.

[0041] Each wavelength division multiplexing device 2 is respectively connected to a detector device 6, which is used to delay the light beam emitted by the light source 1 and detect the returned light beam. The detector device 6 includes a first beam splitter 61, a beam delay line device 62, a three-end circulator 63, a detector 64 and a second beam splitter 65.

[0042] The light source 1 is a frequency-sweeping laser. The light beam emitted by the light source 1 passes through the wavelength division multiplexing device 2 and then passes through the first beam splitter 61 to be divided into a first light beam and a second light beam.

[0043] The first light beam generates a certain amount of optical path difference through the beam delay line device 62, and then is transmitted to the beam combiner 3 through the optical fiber for beam combining, and then enters the sub-aperture devices 4 respectively; the sub-aperture devices 4 are distributed on the surface of one side of the optical system 5 to be measured, and the optical system 5 to be measured is rotated to achieve a comprehensive detection of the optical system 5 to be measured.

[0044] The beam delay line device 62 is composed of a corner reflector and a large field of view coupler to achieve optical path scanning. The present invention uses the wavelength division multiplexing device 2 and the frequency sweeping laser to form a multi-channel selective optical switch to reduce the absolute light intensity required for beacon light emission, and ultimately reduce the nonlinear effects, secondary reflections, and stray light generated inside the optical fiber to improve the detection accuracy of the beacon light guidance.

[0045] When the sub-aperture devices 4 are arranged in a cross shape, the angle of rotation of the optical system 5 to be measured is 90°;

[0046] When the sub-aperture devices 4 are arranged in an equilateral triangle, the rotation angle of the optical system 5 to be measured is 120°;

[0047] The present invention does not limit the arrangement of the sub-aperture devices 4 , and the sub-aperture devices 4 can be arranged in any shape by changing the number of the sub-aperture devices 4 .

[0048] Taking the arrangement of the sub-aperture device 4 as an equilateral triangle as an example, when the arrangement of the sub-aperture device 4 is an equilateral triangle, there is one sub-aperture in the middle and three sub-apertures are evenly distributed around.

[0049] After being emitted from the sub-aperture device 4 , the first light beam irradiates the optical fiber system 5 to be tested and the lens inside it. The generated reflected light beam returns along the original path and is transmitted to the three-end circulator 63 through the second beam splitter 65 .

[0050] The second light beam is emitted from the first beam splitter 61 and then transmitted to the three-terminal circulator 63 through the optical fiber.

[0051] The reflected light beam of the first light beam interferes with the second light beam inside the three-end circulator 63 and then is incident on the detector 64 to obtain interference fringes.

[0052] The present invention uses the principle of partially coherent light interference to obtain the spacing between optical elements at the main interference maximum position, and obtains unknown information such as the position, tilt angle and assembly error of the optical elements in the optical system 5 to be measured through multi-point sampling. The mean of the spectral dispersion stripes is mainly used to track the delay position of the maximum contrast. Phase delay tracking is more demanding because it includes locking the actual phase of the stripes.

[0053] Figure 2 A flow chart of a high-precision long-travel optical interval measurement method based on optical fiber interconnection provided according to an embodiment of the present invention is shown.

[0054] like Figure 2 As shown, the high-precision long-travel optical interval measurement method based on optical fiber interconnection provided by an embodiment of the present invention includes the following steps:

[0055] S1, by controlling the wavelength division multiplexing device and the corner reflector respectively to change the wavelength λ of the i-th first light beamij and optical path difference Δδ ik ;

[0056] S2, the light intensity I of the interference beam of the i-th first light beam and the second light beam received by the detector i The following equation is obtained:

[0057]

[0058] in,

[0059] E i1 and E i2 The intensity of the i-th interference beam is I i The amount of

[0060] δ i is the original optical path of the i-th interference beam;

[0061] δ i0 is the optical path of the i-th interference beam when the additional delay intensity is 0;

[0062] Δλ is the current wavelength λ ij With the previous wavelength λ ij-1 The difference between ij -λ ij-1 ;

[0063] i = 1, 2, 3, ... n;

[0064] j = 1, 2, 3, ... n;

[0065] k = 1, 2, 3, ... n;

[0066] Then we get at least four nonlinear equations:

[0067]

[0068] Perform Fourier transform on the above equations to transform the nonlinear equations into multivariate linear equations and then solve them to obtain E i1 , E i2 , δ i , δ i0 The theoretical optical path difference is calculated based on the existing curvature and refractive index information, and the actual inclination angle and assembly error of the original are solved according to the difference between the optical path difference obtained by interference scanning and the theoretical one.

[0069] S3, after solving the above equation, the characteristic frequency (δ i -δ i0 ), according to the characteristic frequency (δ i -δ i0) The inclination angle and assembly error of the optical system to be tested are calculated by the spherometer principle, and the assembly adjustment of the optical system to be tested is guided according to the calculated assembly error.

[0070] Based on the high detection distribution flexibility characteristics of optical fiber interconnection, the present invention can use the method of rotational time-division multiplexing to improve the detection space sampling rate, and finally directly realize the contour detection of the optical system to be tested. The stability and error suppression of the multi-degree-of-freedom of the mechanism are achieved through the optical closed loop, the pupil posture is constrained based on spatial mechanism, and an open-loop accuracy compensation mechanism is established to reduce the absolute requirements for mechanical accuracy.

[0071] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

[0072] The above specific implementations of the present invention do not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A high-precision, long-travel optical interval measurement device based on optical fiber interconnection, characterized in that: include: Light sources, wavelength division multiplexing devices, beam combiners, sub-aperture devices and detector devices; The light beam emitted by the light source is transmitted to the wavelength division multiplexing device through an optical fiber, and the wavelength division multiplexing device is used to form a detection optical path with different bandwidths. Each of the wavelength division multiplexing devices is connected to a detector device respectively, and the detector device includes a first beam splitter, a beam delay line device, a three-terminal circulator, a detector, and a second beam splitter; The light beam emitted by the light source passes through the wavelength division multiplexing device and then passes through the first beam splitter to be divided into a first light beam and a second light beam; The first light beam generates an optical path difference through the beam delay line device, is transmitted to the beam combiner through an optical fiber for beam combining, and then enters the sub-aperture devices respectively; the sub-aperture devices are distributed on the surface of one side of the optical system to be measured; the sampling rate of the detection space is improved by rotating the optical system to be measured using a rotational time-division multiplexing method; After being emitted by the sub-aperture device, the first light beam irradiates the optical system to be measured and the large-aperture lens inside it, and the generated reflected light beam returns along the original path and is transmitted to the three-end circulator through the second beam splitter; The second light beam is emitted from the first beam splitter and then transmitted to the three-terminal circulator through an optical fiber; The reflected light beam of the first light beam and the second light beam generate an interference light beam inside the three-end circulator and then are incident on the detector to obtain light intensity; the inclination angle and assembly error of the optical system to be measured are calculated according to the light intensity of the interference light beam, and the assembly of the optical system to be measured is guided according to the assembly error.

2. The high-precision long-travel optical interval measuring device based on optical fiber interconnection according to claim 1 is characterized in that: The light source is a frequency-sweeping laser.

3. The high-precision long-travel optical interval measuring device based on optical fiber interconnection according to claim 2 is characterized in that: The beam delay line device consists of a corner reflector and a large field of view coupler.

4. The high-precision long-travel optical interval measuring device based on optical fiber interconnection according to claim 3 is characterized in that: When the sub-aperture devices are arranged in a cross shape, the rotation angle of the optical system to be measured is 90°.

5. The high-precision long-travel optical interval measuring device based on optical fiber interconnection according to claim 4 is characterized in that: When the sub-aperture devices are arranged in an equilateral triangle, the rotation angle of the optical system to be measured is 120°.

6. A measurement method implemented by using the high-precision long-travel optical interval measurement device based on optical fiber interconnection as described in any one of claims 3 to 5, characterized in that: The following steps are involved: S1, by respectively controlling the wavelength division multiplexing device and the corner reflector to change the wavelength λ of the i-th first light beam ij and optical path difference Δδ ik ; S2, the light intensity I of the interference beam of the i-th first light beam and the second light beam received by the detector i The following equation is obtained: in, E i1 and E i2 The intensity of the i-th interference beam is I i The amount of δ i is the original optical path of the i-th interference beam; δ i0 is the optical path of the i-th interference beam when the additional delay intensity is 0; Δλ is the current wavelength λ ij With the previous wavelength λ ij-1 The difference between ij -λ ij-1 ; i = 1, 2, 3, ... n; j = 1, 2, 3, ... n; k = 1, 2, 3, ... n; Then we get at least four nonlinear equations: Perform Fourier transform on the above equations to transform the nonlinear equations into multivariate linear equations and then solve them to obtain E i1 , E i2 , δ i , δ i0 ; S3, after solving the above equations, the characteristic frequency (δ i -δ i0 ), according to the characteristic frequency (δ i -δ i0 ) The inclination angle and assembly error of the optical system to be measured are calculated by the spherometer principle, and the assembly error is used to guide the optical system to be measured to be assembled and adjusted.

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