Apodization ring light source based on fast reflecting mirror regulation and control

Abstract

The invention discloses an apodization ring light source based on fast reflecting mirror regulation and control and a surface shape measurement method. The annular track of the virtual point light source is accurately regulated and controlled through the fast reflecting mirror, a dynamic annular light source and a static apodization point light source can be achieved, and meanwhile the stripe contrast ratio during long interference cavity can be kept. In the dynamic ring light source mode, the fast reflecting mirror regulates and controls the point light source to rotate at a high speed along a circular track with a preset radius to form a virtual ring light source; in the static apodization point light source mode, the fast reflecting mirror regulates and controls the point light source to step to equal division points on a circular trajectory, and multi-point static collection is carried out. Both the two measurement modes can effectively suppress coherent noise, and meanwhile, the long-cavity measurement capability is kept. The light source is simple in structure and high in practicability.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical interference testing, and in particular to an apodized ring light source controlled by a fast-reflection mirror. Background Art

[0002] Phase-shifting interferometers typically use laser sources with high coherence. Due to the high coherence of laser light, surface imperfections and dust in the optical components of the interferometer system can cause significant speckle noise. To suppress this noise, two mainstream approaches are currently available. The first involves inserting a rapidly rotating ground glass at the imaging position to suppress coherent noise through dynamic scattering. However, the use of ground glass degrades the system's modulation transfer function, affecting imaging resolution. The second approach involves constructing a ring light source at the light source position. This ring light source is formed by altering the trajectory of a point light source using a rapidly rotating wedge mirror, or by combining an axicon, an axicon lens, a carbon grayscale lens (CGH), and a rapidly rotating ground glass. The rotating wedge mirror approach is a dynamic ring light source and cannot achieve statically apodized point source measurement mode. The inclusion of ground glass in the axicon approach destroys spatial coherence, compromising fringe contrast during long cavity measurements. Therefore, a method is needed that can achieve both a dynamic ring light source and a statically apodized point light source while maintaining fringe contrast in long interferometer cavities. Summary of the Invention

[0003] The present invention aims to address the aforementioned problems of the prior art by providing an apodized ring light source controlled by a fast-reflection mirror and a surface shape measurement method based on this light source. By controlling the annular trajectory of a virtual point light source through a fast-reflection mirror, both a dynamic ring light source and a static apodized point light source can be realized, while maintaining the fringe contrast of a long interferometer cavity. This method is suitable for use in high-precision, low-noise phase-shifting interferometers.

[0004] The technical solution to achieve the purpose of the present invention is as follows: on the one hand, an apodized ring light source based on fast mirror control is provided, the apodized ring light source includes a light source output module, a light source adjustment module and a long cavity interferometer system;

[0005] The light source output module is used to emit a point light source; the light source module is used to generate a virtual point light source, and to control the spatial position of the point light source by controlling the position of the virtual point light source to form a static point light source or a dynamic ring light source; the long cavity interferometry system is used to realize long cavity interferometry measurement based on the static point light source or the dynamic ring light source.

[0006] Furthermore, the light source emitting module includes a laser and a single-mode optical fiber arranged in sequence along the optical axis; the light source module includes an optical fiber interface and a quick reflector; the laser emits laser light, which passes through the single-mode optical fiber and the optical fiber interface in sequence and then enters the quick reflector; the quick reflector reflects the laser light, and the reverse extension line of the reflected light converges to form a virtual point light source.

[0007] Furthermore, the distance from the optical fiber interface to the quick-reflection mirror is equal to the distance from the virtual point light source to the quick-reflection mirror, ensuring that the actual point light source is conjugate with the virtual point light source.

[0008] Furthermore, the posture of the fast mirror is controlled by an external device so that the virtual point light source rotates at high speed along a circular trajectory or stays at a certain equal point on the circular trajectory, forming a dynamic ring light source or a static point light source, so that the device is in a dynamic ring light source mode or a static point light source mode.

[0009] Furthermore, the long cavity interferometer system includes a beam splitter, a collimator, a reference mirror, a measured mirror, an aperture, an imaging mirror and a planar array detector; the static point light source or the dynamic ring light source is transmitted through the beam splitter, collimated by the collimator, reflected by the reference mirror, and reflected by the measured mirror, and then returns to the reflective surface of the beam splitter. After the reflected light beam is reflected by the beam splitter, it is filtered by the aperture and imaged by the imaging mirror to the planar array detector.

[0010] Furthermore, the distance from the virtual point light source to the beam splitter is equal to the distance from the aperture to the beam splitter, so as to ensure that the virtual point light source is conjugate with the convergence point of the reflected light.

[0011] Furthermore, in the dynamic ring light source mode, the driving frequency of the fast mirror must satisfy: if the single-frame acquisition time of the array detector is T, the fast mirror driving frequency f must satisfy f>1 / T, to ensure that the virtual point light source rotates at least once within the acquisition time of one frame.

[0012] On the other hand, a surface shape measurement method based on the apodized ring light source is provided, the method comprising:

[0013] To perform dynamic ring light mode measurements:

[0014] Step 1: The laser emits laser light, which passes through the single-mode optical fiber, the optical fiber interface, and the fast-reflecting mirror in sequence. The fast-reflecting mirror reflects the laser light, and the reverse extension line of the emitted light converges to form a virtual point light source;

[0015] Step 2: Using an external device to control the posture of the fast mirror, the virtual point light source rotates at high speed along a circular trajectory with a radius of r, forming a virtual ring light source;

[0016] Step 3: The virtual ring light source is sequentially transmitted through the beam splitter, collimated by the collimator, reflected by the reference mirror, and reflected by the measured mirror, and then returns to the reflective surface of the beam splitter; after being reflected by the beam splitter, the reflected light beam is filtered by the aperture and imaged by the imaging mirror to the area array detector;

[0017] Step 4: Set the exposure time of the array detector and collect multiple frames of interference patterns;

[0018] Step 5: Use a phase decomposition algorithm to solve the multi-frame interference pattern collected by the array detector to obtain the shape of the measured mirror surface.

[0019] Furthermore, in step 2, the angle of the fast-reflecting mirror is adjusted by an external device to form a ring-shaped light source with different radii, thereby achieving a variable light source trajectory.

[0020] Furthermore, replace steps 2 to 5 with the following process to perform static point light source mode measurement:

[0021] Step 21, controlling the posture of the fast mirror by an external device so that the virtual point light source stays at a certain equal division point on the circular trajectory, and fixing the posture of the fast mirror;

[0022] Step 31: The virtual ring light source is sequentially transmitted through the beam splitter, collimated by the collimator, reflected by the reference mirror, and reflected by the measured mirror, and then returns to the reflective surface of the beam splitter; after being reflected by the beam splitter, the reflected light beam is filtered by the aperture and imaged by the imaging mirror to the area array detector;

[0023] Step 41, collecting multiple frames of interference patterns at the current equipartition point, and obtaining the measurement results at the current point light source position through a phase deconvolution algorithm;

[0024] Step 51, repeating steps 21 to 41 until all quantiles on the entire circular trajectory are traversed;

[0025] Step 61: average all the measurement results to obtain the measured mirror shape.

[0026] Compared with the prior art, the present invention has the following significant advantages:

[0027] (1) It supports both dynamic ring light source mode and static point light source mode, meeting the coherent noise suppression requirements in various measurement scenarios.

[0028] (2) The fringe contrast of the long interference cavity can be maintained in both light source modes.

[0029] The present invention is further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Schematic diagram of an apodized ring light source controlled by a fast mirror in one embodiment.

[0031] Figure 2 Schematic diagram of a point light source trajectory in an embodiment. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of this application more clear, the following further describes this application in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0033] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indications will also change accordingly.

[0034] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features specified as "first" and "second" may explicitly or implicitly include at least one of such features. In addition, the technical solutions between the various embodiments can be combined with each other, but this must be based on the fact that ordinary technicians in this field can implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0035] In one embodiment, combined Figure 1 , provides an apodization ring light source based on fast mirror control, the apodization ring light source includes a light source output module, a light source adjustment module 13 and a long cavity interferometer system;

[0036] The light source output module is used to emit a point light source; the light source module 13 is used to generate a virtual point light source 5, and to control the spatial position of the point light source by adjusting the position of the virtual point light source 5 to form a static point light source or a dynamic ring light source; the long cavity interferometry system is used to realize long cavity interferometry measurement based on a static point light source or a dynamic ring light source.

[0037] Furthermore, in one embodiment, the light source emitting module includes a laser 1 and a single-mode optical fiber 2 arranged in sequence along the optical axis; the light source module 13 includes an optical fiber interface 3 and a quick reflector 4; the laser 1 emits laser light, which passes through the single-mode optical fiber 2 and the optical fiber interface 3 in sequence and then enters the quick reflector 4; the quick reflector 4 reflects the laser light, and the reverse extension line of the reflected light converges to form a virtual point light source 5.

[0038] Here, the fast mirror 4 is an optical device that uses piezoelectric ceramics or voice coil motors to quickly deflect the light beam at a small angle. Through control software, the virtual point light source (5) can be adjusted to form a circular motion trajectory, forming a variable-track ring light source.

[0039] Preferably, in some embodiments, the distance from the optical fiber interface 3 to the quick-reflection mirror 4 is equal to the distance from the virtual point light source 5 to the quick-reflection mirror 4 , ensuring that the actual point light source is conjugate with the virtual point light source.

[0040] Preferably, in some embodiments, the posture of the fast mirror 4 is controlled by an external device, so that the virtual point light source 5 rotates at high speed along a circular trajectory or stays at a certain equal point on the circular trajectory, forming a dynamic ring light source or a static point light source such as Figure 2 As shown, the device is in dynamic ring light mode or static point light mode.

[0041] Here, the external device may be computer software.

[0042] Furthermore, in one embodiment, the long cavity interferometer system includes a beam splitter 6, a collimating mirror 7, a reference mirror 8, a measured mirror 9, an aperture 10, an imaging mirror 11 and a planar array detector 12; the static point light source or the dynamic ring light source is transmitted through the beam splitter 6, collimated by the collimating mirror 7, reflected by the reference mirror 8, and reflected by the measured mirror 9, and then returns to the reflecting surface of the beam splitter 6. After the reflected light beam is reflected by the beam splitter 6, it is filtered by the aperture 10 and imaged by the imaging mirror 11 to the planar array detector 12.

[0043] Preferably, in some embodiments, the distance from the virtual point light source 5 to the beam splitter 6 is equal to the distance from the aperture 10 to the beam splitter 6 to ensure that the virtual point light source 5 is conjugate with the convergence point of the reflected light.

[0044] Preferably, in some embodiments, in the dynamic ring light source mode, the driving frequency of the fast mirror 4 needs to satisfy: if the single-frame acquisition time of the array detector 12 is T, the driving frequency f of the fast mirror 4 needs to satisfy f>1 / T, so as to ensure that the virtual point light source 5 rotates at least once within the acquisition time of one frame.

[0045] For example, if the time required for the array detector to collect one frame of interference pattern is 10 ms, then the fast mirror control frequency must be greater than f = 1 / T = 100 Hz.

[0046] In one embodiment, a surface shape measurement method based on an apodized ring light source is proposed, the method comprising:

[0047] To perform dynamic ring light mode measurements:

[0048] Step 1: Laser 1 emits laser light, which passes through single-mode fiber 2, fiber interface 3, and quick-reflection mirror 4 in sequence. Quick-reflection mirror 4 reflects the laser light, and the reverse extension line of the emitted light converges to form a virtual point light source 5;

[0049] Step 2: The posture of the fast mirror 4 is controlled by an external device so that the virtual point light source 5 rotates at high speed along a circular trajectory with a radius r, forming a virtual ring light source;

[0050] Step 3: The virtual ring light source is sequentially transmitted through the beam splitter 6, collimated by the collimator 7, reflected by the reference mirror 8, and reflected by the measured mirror 9, and then returns to the reflective surface of the beam splitter 6; after being reflected by the beam splitter 6, the reflected light beam is filtered by the aperture 10 and imaged by the imaging mirror 11 to the area array detector 12;

[0051] Step 4: setting the exposure time of the area array detector 12 to collect multiple frames of interference patterns;

[0052] Step 5: Use a phase deconvolution algorithm to solve the multi-frame interference pattern collected by the area array detector 12 to obtain the surface shape of the measured mirror 9.

[0053] Here, in step 2, the angle of the fast-reflecting mirror 4 is adjusted by an external device to form annular light sources with different radii, thereby achieving variable light source traces.

[0054] Furthermore, replace steps 2 to 5 with the following process to perform static point light source mode measurement:

[0055] Step 21, controlling the posture of the quick-reflection mirror 4 by an external device so that the virtual point light source 5 stops at a certain equal-division point on the circular trajectory, and fixing the posture of the quick-reflection mirror 4;

[0056] Step 31: The virtual ring light source is sequentially transmitted through the beam splitter 6, collimated by the collimator 7, reflected by the reference mirror 8, and reflected by the measured mirror 9, and then returns to the reflective surface of the beam splitter 6; after being reflected by the beam splitter 6, the reflected light beam is filtered by the aperture 10 and imaged by the imaging mirror 11 to the area array detector 12;

[0057] Step 41, collecting multiple frames of interference patterns at the current equipartition point, and obtaining the measurement results at the current point light source position through a phase deconvolution algorithm;

[0058] Step 51, repeating steps 21 to 41 until all quantiles on the entire circular trajectory are traversed;

[0059] Step 61: average all the measurement results to obtain the surface shape of the measured mirror 9. The obtained result is the final result after suppressing the coherent noise.

[0060] In summary, the light source and method of the present invention are simple and easy to implement. Their core advantage lies in the precise control of the position of the virtual point light source by a fast mirror, forming a variable-track ring light source. This effectively suppresses coherent noise while maintaining fringe contrast in the long interferometer cavity. Furthermore, it is compatible with both dynamic ring light source measurement mode and static apodized point light source measurement mode, making it suitable for a variety of measurement scenarios.

[0061] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only illustrative of the principles of the present invention. Without departing from the spirit and scope of the present invention, any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included in the scope of protection of the present invention.

Claims

1. An apodized ring light source based on fast mirror control, characterized in that: The apodization ring light source comprises a light source emission module, a light source adjustment module (13) and a long cavity interference system; The light source emitting module is used to emit a point light source; the light source module (13) is used to generate a virtual point light source (5), and to regulate the spatial position of the point light source by regulating the position of the virtual point light source (5) to form a static point light source or a dynamic ring light source; the long cavity interferometry system is used to realize long cavity interferometry measurement based on the static point light source or the dynamic ring light source.

2. The apodized ring light source based on fast mirror control according to claim 1, characterized in that: The light source emission module comprises a laser (1) and a single-mode optical fiber (2) arranged in sequence along an optical axis; the light source module (13) comprises an optical fiber interface (3) and a quick-reflection mirror (4); the laser (1) emits laser light, which passes through the single-mode optical fiber (2) and the optical fiber interface (3) in sequence and then enters the quick-reflection mirror (4); the quick-reflection mirror (4) reflects the laser light, and the reverse extension line of the reflected light converges to form a virtual point light source (5).

3. The apodized ring light source based on fast mirror control according to claim 2, characterized in that: The posture of the fast-reflecting mirror (4) is controlled by an external device, so that the virtual point light source (5) rotates at high speed along a circular trajectory or stays at a certain equal-division position on the circular trajectory, forming a dynamic ring light source or a static point light source, so that the device is in a dynamic ring light source mode or a static point light source mode.

4. The apodized ring light source based on fast mirror control according to claim 3, characterized in that: The long cavity interferometer system comprises a beam splitter (6), a collimator (7), a reference mirror (8), a measured mirror (9), an aperture (10), an imaging mirror (11) and a planar array detector (12); the static point light source or the dynamic ring light source is transmitted through the beam splitter (6), collimated by the collimator (7), reflected by the reference mirror (8), and reflected by the measured mirror (9), and then returns to the reflection surface of the beam splitter (6); after the reflected light beam is reflected by the beam splitter (6), it is filtered by the aperture (10) and imaged by the imaging mirror (11) to the planar array detector (12).

5. The apodized ring light source based on fast mirror control according to claim 3, characterized in that: In the dynamic ring light source mode, the driving frequency of the fast mirror (4) must satisfy: if the single-frame acquisition time of the array detector (12) is T, the driving frequency f of the fast mirror (4) must satisfy f>1 / T, so as to ensure that the virtual point light source (5) rotates at least once within the acquisition time of one frame.

6. The surface shape measurement method of the apodized ring light source according to any one of claims 1 to 5, characterized in that: The method comprises: To perform dynamic ring light mode measurements: Step 1: The laser (1) emits laser light, which passes through the single-mode optical fiber (2), the optical fiber interface (3), and the fast-reflecting mirror (4) in sequence. The fast-reflecting mirror (4) reflects the laser light, and the reverse extension line of the emitted light converges to form a virtual point light source (5); Step 2, controlling the posture of the fast-reflecting mirror (4) by an external device so that the virtual point light source (5) rotates at high speed along a circular trajectory with a radius of r, thereby forming a virtual ring light source; Step 3, the virtual ring light source is sequentially transmitted through the beam splitter (6), collimated by the collimator (7), reflected by the reference mirror (8), and reflected by the measured mirror (9), and then returns to the reflection surface of the beam splitter (6); after the reflected light beam is reflected by the beam splitter (6), it is filtered by the aperture (10) and imaged by the imaging mirror (11) to the area array detector (12); Step 4, setting the exposure time of the array detector (12) and collecting multiple frames of interference patterns; Step 5, using a phase resolution algorithm to resolve the multi-frame interference pattern collected by the array detector (12) to obtain the surface shape of the measured mirror (9).

7. The surface shape measurement method according to claim 6, characterized in that: In step 2, the angle of the fast-reflecting mirror (4) is adjusted by an external device to form a ring light source with different radii, thereby achieving variable light source traces.

8. The surface shape measurement method according to claim 6, characterized in that: Replace steps 2 to 5 with the following procedure to perform static point source mode measurements: Step 21, regulating the posture of the quick-reflection mirror (4) through an external device so that the virtual point light source (5) stays at a certain equal-division position on the circular trajectory, and fixing the posture of the quick-reflection mirror (4); Step 31, the virtual ring light source is sequentially transmitted through the beam splitter (6), collimated by the collimator (7), reflected by the reference mirror (8), and reflected by the measured mirror (9), and then returns to the reflection surface of the beam splitter (6); after being reflected by the beam splitter (6), the reflected light beam is filtered by the aperture (10) and imaged by the imaging mirror (11) to the area array detector (12); Step 41, collecting multiple frames of interference patterns at the current equipartition point, and obtaining the measurement results at the current point light source position through a phase deconvolution algorithm; Step 51, repeating steps 21 to 41 until all quantiles on the entire circular trajectory are traversed; Step 61, average all the measurement results to obtain the surface shape of the measured mirror (9).

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