Angle Adjustment Device and Method for Separating the First-Order and Zero-Order Spectra in Off-Axis Digital Holography

Abstract

The present invention relates to an angle adjustment device and method for separating the first-order and zero-order spectra in off-axis digital holography, comprising: a base sleeved on a rotating shaft and detachably mounted on a platform, the base being rotatable about the rotating shaft; a shaft rod mounted at the top of the base and arranged horizontally; a connecting member sleeved on the shaft rod and rotatable about the shaft rod; a fixing plate mounted at one end of the connecting member away from the shaft rod; and a lens mounted on one side of the fixing plate away from the connecting member. In the present invention, the angle adjustment is divided into two independent directions without interference, so as to accurately control the tilting posture of the lens, thereby being able to conveniently adjust the position of the first-order spectrum and make the best use of the frequency domain space in holographic interferometric measurement.

Description

Technical Field

[0001] The present invention relates to the technical field of off-axis digital holography, and in particular to an angle adjustment device and method for separating first-order and zero-order spectra in off-axis digital holography. Background Art

[0002] Digital holographic interferometry is an interferometric measurement method that divides the laser light source into two beams. One beam irradiates the surface of the sample to be tested with a certain spot size, is received by the camera in the form of reflection or transmission, and interferes with the other reference light to form a holographic interference pattern, which is recorded by the CCD camera. The complex wavefront of the object light wave carrying the phase modulation information of the sample surface is separated from the intensity pattern, and then the intensity and phase of the sample to be tested are obtained. It has been widely used in the fields of biological cell detection, meta-lens detection, MEMS vibration mode, etc.

[0003] Digital holography is mainly divided into two measurement optical paths: on-axis digital holography and off-axis digital holography. In on-axis digital holography, a specific phase shift value is introduced into the reference light to construct a set of equations to obtain the sample modulation phase information. In off-axis digital holography, a carrier frequency is introduced by tilting the reference light at an angle to form an angle with the object light modulated by the sample. In the spectrum diagram after Fourier transformation of the interference pattern, the ±1-order spectrum is separated from the 0-order spectrum, and the 1-order spectrum is extracted and moved to the center of the spectrum. The complex wavefront information corresponding to the sample can be obtained by inverse Fourier transformation, thereby obtaining the intensity and phase information of the sample.

[0004] In off-axis digital holography, the separation of the 1st-order spectrum and the 0th-order spectrum is a prerequisite for accurately solving the complex wavefront of the object light wave from the holographic interference pattern. In the design of the off-axis digital holography system, the position of the 1st-order spectrum can be controlled by the angle between the reference light and the object light. However, the change in the size of the angle has a great influence on the position of the 1st-order spectrum, and a high requirement is placed on the design accuracy of the angle. In practical applications, it is difficult to achieve the accurate realization of the angle through the design and assembly of parts.

[0005] Commonly used adjustment devices often adjust the angle by adjusting the fine-tuning screws and adjusting the displacement of screws distributed at different positions, but adjusting a screw often causes angle changes in two directions, making it difficult to adjust the first-level spectrum to the diagonal position in the frequency domain to achieve maximum utilization of the frequency domain space. Therefore, how to conveniently adjust the position of the first-level spectrum to achieve an ideal spectrum separation effect is a technical problem that needs to be solved in this application. Summary of the invention

[0006] The purpose of the present invention is to overcome the defects of the prior art and to provide an angle adjustment device and method for separating the 1st and 0th order spectra in off-axis digital holography, so as to solve the problem that it is difficult for the existing adjustment device to adjust the 1st order spectrum to the diagonal position in the frequency domain.

[0007] To achieve the above object, the present invention provides an angle adjustment device for separating the first-order and zero-order spectra in off-axis digital holography, which is installed on a platform. A rotating shaft is vertically provided on the platform. The angle adjustment device includes:

[0008] A base sleeved on the rotating shaft and detachably installed on the platform, and the base can rotate around the rotating shaft;

[0009] A shaft rod installed at the top end of the base and arranged horizontally;

[0010] A connecting member sleeved on the shaft rod and capable of rotating around the shaft rod;

[0011] A fixing plate installed at one end of the connecting member away from the shaft rod;

[0012] A lens installed on one side of the fixing plate away from the connecting member;

[0013] A slot horizontally penetrating the base is provided at the top end of the base, and a abutting plate and an elastic pressing plate are respectively formed on both sides of the slot;

[0014] The connecting member is inserted into the slot;

[0015] The shaft rod includes a rod portion and a head portion fixedly connected to one end of the rod portion. The head portion is located outside the pressing plate. The rod portion passes through the pressing plate, the connecting member and the abutting plate and partially extends out of the abutting plate to form an outer extending portion;

[0016] The angle adjustment device further includes a limiting member sleeved and threadedly connected to the outer extending portion. By screwing the limiting member, the head portion is pressed against the pressing plate, so that the pressing plate is elastically deformed under pressure, thereby clamping and fixing the connecting member between the pressing plate and the abutting plate.

[0017] In the present invention, by rotating and adjusting the base, the lens can be rotated and adjusted in the horizontal direction. By rotating the connecting member around the shaft rod, the pitching angle of the lens can be adjusted. By dividing the angle adjustment into two independent adjustments in the horizontal direction and the pitching direction, without interference, the deflection angles of the lens in the horizontal and pitching directions can be adjusted more precisely, so as to conveniently adjust the position of the first-order spectrum to the diagonal line of the frequency domain space and achieve an ideal spectrum separation effect.

[0018] A further improvement of the angle adjustment device for separating the first-order and zero-order spectra in off-axis digital holography of the present invention is that the base includes a vertical plate sleeved on the rotating shaft and arranged vertically and a horizontal plate vertically connected to the bottom end of the vertical plate;

[0019] The horizontal plate is detachably installed on the platform.

[0020] A further improvement of the angle adjustment device for separating the first-order and zero-order spectra in off-axis digital holography of the present invention lies in that at least one waist-shaped hole is penetrated through the horizontal plate, and the waist-shaped hole is in an arc shape with the rotation axis as the center of the circle;

[0021] The base is mounted and fixed on the platform by passing a fastener through the waist-shaped hole and fixing it on the platform.

[0022] A further improvement of the angle adjustment device for separating the first-order and zero-order spectra in off-axis digital holography of the present invention lies in that there are two waist-shaped holes which are distributed at intervals, and the center lines of the two waist-shaped holes are aligned.

[0023] A further improvement of the angle adjustment device for separating the first-order and zero-order spectra in off-axis digital holography of the present invention lies in that a shaft hole adapted to the rotation axis and arranged vertically is provided on the bottom surface of the vertical plate, and the rotation axis is inserted into the shaft hole.

[0024] A further improvement of the angle adjustment device for separating the first-order and zero-order spectra in off-axis digital holography of the present invention lies in that the cross-sectional dimension of the end head is larger than that of the rod part.

[0025] A further improvement of the angle adjustment device for separating the first-order and zero-order spectra in off-axis digital holography of the present invention lies in that a first through hole adapted to the rod part is provided on the pressing plate, and the rod part passes through the first through hole.

[0026] A further improvement of the angle adjustment device for separating the first-order and zero-order spectra in off-axis digital holography of the present invention lies in that the abutting plate is provided with a second through hole adapted to the rod part and aligned with the first through hole, and the rod part passes through the second through hole.

[0027] The present invention also provides an adjustment method for the angle adjustment device for separating the first-order and zero-order spectra in off-axis digital holography as described above, including the following steps:

[0028] By rotating and adjusting the base to drive the lens to rotate in the horizontal direction, and by rotating and adjusting the connecting member to make the lens rotate around the shaft rod, the lens is adjusted to rotate in the pitching direction manually or electrically, so as to adjust the positions of the first-order and zero-order spectra in the spectrogram of the holographic interference pattern and achieve the effect of ideal spectral separation. Description of the Drawings

[0029] Figure 1 It is a front perspective view of the angle adjustment device for separating the first-order and zero-order spectra in off-axis digital holography of the present invention.

[0030] Figure 2Side view of the angle adjustment device for separating the first - order and zero - order spectra in off - axis digital holography of the present invention.

[0031] Figure 3 Top view of the angle adjustment device for separating the first - order and zero - order spectra in off - axis digital holography of the present invention.

[0032] Figure 4 Spectrum diagram after Fourier transform of the measured holographic interference pattern of the angle adjustment device for separating the first - order and zero - order spectra in off - axis digital holography of the present invention.

[0033] Symbol description: base 10, vertical plate 11, shaft hole 111, slot 112, pressing plate 113, abutting plate 114, horizontal plate 12, waist - shaped round hole 121, shaft rod 20, end head 21, rod part 22, connecting piece 30, fixing plate 40, limiting piece 50, platform 60, rotating shaft 70. Detailed implementation manners

[0034] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0035] Aiming at the problem of the existing angle adjustment device that adjusting a certain screw causes angle changes in multiple directions and it is difficult to adjust the first - order spectrum in the spectrum diagram obtained by digital holographic interference to the diagonal position in the frequency domain space, the present invention provides an angle adjustment device and method for separating the first - order and zero - order spectra in off - axis digital holography, including a base 10, a shaft rod 20, a connecting piece 30, a fixing plate 40 and a lens, which can separately adjust the angles of the lens in the horizontal and pitching directions, and can make the frequency domain space in holographic interference measurement be utilized to the greatest extent, and obtain measurement results with higher precision requirements.

[0036] The following will describe the angle adjustment device and method for separating the first - order and zero - order spectra in off - axis digital holography of the present invention with reference to the accompanying drawings.

[0037] See Figure 1 and Figure 3, in this embodiment, an angular adjustment device for separating the first-order and zero-order spectra in off-axis digital holography is installed on a platform 60. A rotating shaft 70 is vertically provided on the platform 60. The angular adjustment device includes: a base 10 sleeved on the rotating shaft 70 and detachably installed on the platform 60, and the base 10 can rotate around the rotating shaft 70; a shaft rod 20 installed at the top of the base 10 and arranged horizontally; a connecting member 30 sleeved on the shaft rod 20 and capable of rotating around the shaft rod 20; a fixing plate 40 installed at one end of the connecting member 30 away from the shaft rod 20; and a lens installed on one side of the fixing plate 40 away from the connecting member 30.

[0038] In this embodiment, the angular adjustment device rotates the base 10 around the vertically arranged rotating shaft 70, thereby driving the fixing plate 40 and the lens thereon to rotate, so as to realize the rotational adjustment of the lens in the horizontal direction. By rotating the connecting member 30 around the horizontally arranged shaft rod 20, the fixing plate 40 and the lens thereon are driven to rotate around the shaft rod 20, thereby realizing the angular adjustment of the lens in the pitching direction. The adjustment of the angle is divided into two independent directions without interference, so as to accurately control the horizontal and pitching angles of the lens, and thus the position of the first-order spectrum can be conveniently adjusted to make the best use of the frequency domain space in holographic interferometric measurement.

[0039] See Figure 1 and Figure 2 , in a specific embodiment, the base 10 includes a vertical plate 11 sleeved on the rotating shaft 70 and arranged vertically and a horizontal plate 12 vertically connected to the bottom end of the vertical plate 11, and the horizontal plate 12 is detachably installed on the platform 60. Preferably, the bottom surface of the horizontal plate 12 is flush with the bottom surface of the vertical plate 11.

[0040] See Figure 1 and Figure 3 , further, at least one waist-shaped hole 121 is provided through the horizontal plate 12, and the waist-shaped hole 121 is in an arc shape with the rotating shaft 70 as the center; fasteners are passed through the waist-shaped hole 121 and fixed to the platform 60 to install and fix the base 10 on the platform 60.

[0041] Since the installation position of the fastener on the platform 60 is fixed, by screwing the fastener to release the locking of the fastener on the horizontal plate 12, the base 10 can rotate around the rotating shaft 70. While the horizontal plate 12 rotates, the fastener can slide in the waist-shaped hole 121. When the base 10 rotates to a suitable position, screw the fastener to tighten the base 10. According to the size of the horizontal deflection angle, the waist-shaped hole 121 is designed to adjust the horizontal deflection angle with the rotating shaft 70 as the center.

[0042] See Figure 3, preferably, there are two waist-shaped holes 121 which are spaced apart, and the center lines of the two waist-shaped holes 121 are aligned, so that the base 10 is horizontally fixed on the platform 60. When the base 10 is rotated, only the position adjustment of the base 10 in the horizontal direction can be realized, so as to ensure that while the position in the vertical direction remains unchanged, the positions of the first-order spectrum and the zero-order spectrum in the spectral diagram of the holographic interference pattern are adjusted in the horizontal direction.

[0043] See Figure 1 , preferably, a shaft hole 111 which is adapted to the rotating shaft 70 and is vertically arranged is provided on the bottom surface of the vertical plate 11, and the rotating shaft 70 is inserted into the shaft hole 111.

[0044] See Figure 1 and Figure 3 , in a specific embodiment, a slot 112 penetrating the base 10 horizontally is provided at the top end of the base 10, and a abutting plate 114 and an elastic pressing plate 113 are respectively formed on both sides of the slot 112; the connecting member 30 is inserted into the slot 112; the shaft rod 20 includes a rod portion 22 and a head portion 21 fixedly connected to one end of the rod portion 22, the head portion 21 is located outside the pressing plate 113, the rod portion 22 passes through the pressing plate 113, the connecting member 30 and the abutting plate 114 and partially extends out of the abutting plate 114 to form an outer extending portion; the angle adjusting device further includes a limiting member 50 sleeved and threadedly connected to the outer extending portion. By screwing the limiting member 50, the head portion 21 is pressed against the pressing plate 113, so that the pressing plate 113 is elastically deformed under pressure, so that the connecting member 30 is clamped and fixed between the pressing plate 113 and the abutting plate 114, so as to prevent the position of the connecting member 30 from loosening after vibration and causing the rotation of the fixing plate 40, and further avoid the slight deviation of the angle caused by vibration.

[0045] Preferably, the thickness of the pressing plate 113 is relatively thin and has a certain elasticity. When the limiting member 50 is screwed in the direction close to the head portion 21, the distance between the limiting member 50 and the head portion 21 is reduced, so that the head portion 21 approaches the pressing plate 113 and the pressing plate 113 is inclined and deformed in the direction of the connecting member 30 under pressure, so that the connecting member 30 is clamped and fixed between the pressing plate 113 and the abutting plate 114 to realize the locking of the connecting member 30. When the limiting member 50 is screwed in the direction away from the head portion 21, the distance between the limiting member 50 and the head portion 21 is increased, the head portion 21 is separated from the pressing plate 113, and the pressing plate 113 is no longer tightly pressed on the connecting member 30, so as to release the locking of the connecting member 30, so that the connecting member 30 can rotate and adjust around the shaft rod 20.

[0046] See Figure 1 , further, the cross-sectional dimension of the head portion 21 is larger than that of the rod portion 22, so that the head portion 21 can abut against the pressing plate 113.

[0047] See Figure 1, Further, a first through hole adapted to the rod portion 22 is provided on the pressing plate 113, and the rod portion 22 passes through the first through hole.

[0048] See Figure 1 , Further, a second through hole adapted to the rod portion 22 and aligned with the first through hole is provided on the abutting plate 114, and the rod portion 22 passes through the second through hole.

[0049] Preferably, the shaft rod 20 is a screw.

[0050] Preferably, the fastener is a screw and the limiting member 50 is a nut.

[0051] See Figure 1 and Figure 4 , The present invention also provides an adjustment method for an angle adjustment device for separating the 1st order and 0th order spectra in off-axis digital holography as described above, including the following steps:

[0052] By rotating the adjustment base 10 to drive the lens to rotate in the horizontal direction, and by rotating the adjustment connecting member 30 to make the lens rotate around the shaft rod 20, so as to adjust the lens to a suitable position to realize the position adjustment of the 1st order spectrum and the 0th order spectrum in the spectrogram of the holographic interference pattern.

[0053] In a specific embodiment, when adjusting the rotation of the lens in the horizontal direction, screw the fastener to release the locking of the base 10 by the fastener, rotate the base 10 to rotate and adjust the lens in the horizontal direction, so as to realize the position adjustment of the 1st order spectrum and the 0th order spectrum in the spectrogram of the holographic interference pattern in the horizontal direction. After completing the adjustment in the horizontal direction, screw the fastener to lock and fix the base 10.

[0054] When making the lens rotate around the shaft rod 20, screw the limiting member 50 to release the locking of the connecting member 30, rotate the connecting member 30 to make the lens rotate around the shaft rod 20, so as to realize the position adjustment of the 1st order spectrum and the 0th order spectrum in the spectrogram of the holographic interference pattern in the vertical direction. After completing the adjustment in the vertical direction, screw the limiting member 50 so that the connecting member 30 is clamped and fixed between the pressing plate 113 and the abutting plate 114.

[0055] See Figure 1 and Figure 4 , The following describes the operation process of the angle adjustment device for separating the 1st order and 0th order spectra in off-axis digital holography of the present invention.

[0056] First step: Determine the angle ranges to be adjusted in the horizontal and pitch directions, which are ±5° horizontally and ±5° pitch-wise in this example. Second step: Determine the size and shape of the lens to be pasted, and design the size and shape of the fixing plate 40 according to the size and shape of the lens, usually designed to be the same. In this example, the shape of the fixing plate 40 is square, with a size of 25.4 mm × 25.4 mm. Third step: Fix the fixing plate 40 with screws. Fourth step: Design a shaft hole 111 on the base 10 so that the base 10 can rotate around this axis. The size of the shaft hole 111 of the base 10 is Fifth step: Design an oblong hole 121 on the base 10 so that the proposed device can horizontally deflect around the axis within a certain angle range. In this example, the horizontal angle deflection range is ±5°. In this way, it can be ensured that the device can generate angular deflections in the horizontal and pitch directions, realizing the separation of the first-order spectrum and the zero-order spectrum in off-axis digital holography.

[0057] The specific implementation of the angle adjustment device is as follows: Paste the lens on the fixing plate 40 with glue. After it is completely cured, fix the fixing plate 40 on the base 10 with screws, and fix the base 10 on the platform 60. There is a fixed shaft on the platform 60, which is matched with the shaft hole 111 on the base 10. There are two screw holes along the optical path center line that match the position and hole size of the oblong hole 121 on the base 10 to fix the base 10. After assembly, rotate the base 10 to adjust the positions of the first-order spectrum and the zero-order spectrum in the horizontal direction in the frequency spectrum diagram of the holographic interference pattern. After adjusting to the appropriate position, fix the base 10 with screws. Loosen the screws fixing the fixing plate 40, adjust the pitch angle of the fixing plate 40, and adjust the positions of the first-order spectrum and the zero-order spectrum in the vertical direction in the frequency spectrum diagram of the holographic interference pattern. After adjusting to the appropriate position, tighten the fixing plate 40 with screws. To prevent the rotation of the fixing plate 40, fix it with nuts to provide a prestress to the screws.

[0058] By adopting the above technical solutions, the present invention has the following beneficial effects:

[0059] 1). The adjustment method of the present invention divides the adjustment of the reference light angle into the adjustment of the horizontal and pitch angles to make the most of the frequency domain space in holographic interference measurement.

[0060] 2). The structure of the angle adjustment device of the present invention is very simple, convenient to adjust, and it is very easy to adjust the off-axis angle of the reference light;

[0061] 3). The angle adjustment device of the present invention can well eliminate the angular change caused by vibration to eliminate the measurement error introduced by the angular change during the measurement process.

[0062] It should be noted that the structures, proportions, sizes, etc. shown in the drawings of this specification are only used to cooperate with the content disclosed in the specification for those familiar with this technology to understand and read, and are not used to limit the conditions for the implementation of the present invention. Therefore, they do not have substantial technical significance. Any modification of the structure, change of the proportional relationship or adjustment of the size, without affecting the effects that the present invention can produce and the purposes that can be achieved, should still fall within the scope that can be covered by the technical content disclosed in the present invention. At the same time, the terms such as "upper", "lower", "left", "right", "middle" and "one" cited in this specification are only for the convenience of clear narration, and are not used to limit the scope for the implementation of the present invention. The change or adjustment of their relative relationship, without substantial change in the technical content, should also be regarded as the scope for the implementation of the present invention.

Claims

1. An angular adjustment device for separating the first-order and zero-order spectra in off-axis digital holography, which is installed on a platform. A rotating shaft is vertically provided on the platform, and it is characterized in that, The angle adjustment device includes: A base sleeved on the rotating shaft and detachably mounted on the platform, and the base can rotate around the rotating shaft; A shaft rod installed at the top end of the base and arranged horizontally; A connecting piece sleeved on the shaft rod and capable of rotating around the shaft rod; A fixing plate installed at one end of the connecting piece away from the shaft rod; A lens installed on one side of the fixing plate away from the connecting piece; At the top end of the base, there is a slot horizontally penetrating the base, and a abutting plate and an elastic pressing plate are respectively formed on both sides of the slot; The connecting piece is inserted into the slot; The shaft rod includes a rod portion and a head portion fixedly connected to one end of the rod portion, the head portion is located outside the pressing plate, the rod portion passes through the pressing plate, the connecting piece and the abutting plate and partially extends outside the abutting plate to form an extending portion; The angle adjustment device further includes a limiting member sleeved and threadedly connected to the extending portion. By screwing the limiting member, the head portion is pressed against the pressing plate, so that the pressing plate is elastically deformed under pressure, thereby clamping and fixing the connecting piece between the pressing plate and the abutting plate.

2. The angular adjustment device for separating the first-order and zero-order spectra in off-axis digital holography according to claim 1, characterized in that, The base includes a vertical plate sleeved on the rotating shaft and arranged vertically and a horizontal plate vertically connected to the bottom end of the vertical plate; The horizontal plate is detachably mounted on the platform.

3. The angular adjustment device for separating the first-order and zero-order spectra in off-axis digital holography according to claim 2, characterized in that, At least one waist-shaped hole is penetrated through the horizontal plate, and the waist-shaped hole is in an arc shape with the rotating shaft as the center of the circle; The base is mounted and fixed on the platform by a fastener passing through the waist-shaped hole and fixed on the platform.

4. The angular adjustment device for separating the first-order and zero-order spectra in off-axis digital holography according to claim 3, characterized in that There are two waist-shaped holes and they are spaced apart, and the center lines of the two waist-shaped holes are aligned.

5. The angular adjustment device for separating the first-order and zero-order spectra in off-axis digital holography according to claim 2, wherein, The bottom surface of the vertical plate is provided with a shaft hole adapted to the rotating shaft and arranged vertically, and the rotating shaft is inserted into the shaft hole.

6. The angular adjustment device for separating the first-order and zero-order spectra in off-axis digital holography according to claim 1, wherein, The cross-sectional dimension of the head portion is larger than that of the rod portion.

7. The angular adjustment device for separating the first-order and zero-order spectra in off-axis digital holography according to claim 1, characterized in that, The pressing plate is provided with a first through hole adapted to the rod portion, and the rod portion passes through the first through hole.

8. The angular adjustment device for separating the first-order and zero-order spectra in off-axis digital holography according to claim 7, characterized in that The abutting plate is provided with a second through hole adapted to the rod portion and aligned with the first through hole, and the rod portion passes through the second through hole.

9. A method for adjusting an off-axis digital holographic 1st - order and 0th - order spectrum separation angle adjusting device as described in claim 1, characterized in that, It includes the following steps: By rotating and adjusting the base, the lens is driven to rotate in the horizontal direction, and by rotating and adjusting the connecting piece, the lens is rotated around the shaft rod, so as to adjust the lens to a suitable position to realize the position adjustment of the first-order spectrum and the zero-order spectrum in the spectrogram of the holographic interference pattern.

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