Off-axis holographic beam combining apparatus based on missing mirror and method thereof

Abstract

The application discloses a kind of off-axis holographic beam combining device and method based on missing mirror.It uses missing mirror to combine sample light and reference light, without any obstruction to sample light during beam combining, only reflecting reference light, which can realize perfect beam combining scheme without loss of light intensity, and is more conducive to realizing off-axis holography of reference light and sample light;Through missing mirror, the coincidence of sample light and reference light in off-axis holographic optical path, which is difficult to adjust, and the adjustment of off-axis angle between sample light and reference light on the detector can be realized, and the two problems are completely separated and independently adjusted.By adjusting the placement frame of the missing mirror, the spatial coincidence of the reference light and the sample light on the detection surface can be realized.By adjusting the position of the reference light irradiated to the missing mirror, the off-axis angle between the sample light and the reference light can be adjusted.The application has low cost, is suitable for any spot system, and does not need to rebuild the optical path when the spot changes.

Description

Technical Field

[0001] This invention relates to off-axis holography, specifically to an off-axis holographic beam combining device and method based on a missing mirror. Background Technology

[0002] Today, holography is one of the important means to simultaneously obtain the intensity and phase of light waves. It records and reproduces information about an object holographically through methods such as interference and diffraction, and can completely reproduce the wavefront of the object. It has been widely used in many fields such as microscopy and sensing. Depending on whether there is an angle between the reference light and the sample light during holographic recording, holography can be divided into coaxial holography and off-axis holography. In coaxial holography, the object light wave and the reference light wave propagate in the same direction, and the optical path is simple, but there are two problems. First, the reproduced original image and conjugate image cannot be separated, resulting in the "twin image" problem, that is, an original image (virtual image) and a conjugate image (real image) are symmetrically located on both sides of the hologram. Second, the zero-order term generated by interference introduces a large background noise, resulting in low image contrast. Off-axis holography uses a certain angle between the sample light and the reference light, which enables the separation of the original image, conjugate image, and zero-order term, and solves the problems of twin images and background noise. However, the off-axis angle of off-axis holography has a great influence on the experimental results, and the optical path adjustment of the off-axis angle is relatively complicated.

[0003] Currently, beam splitters are widely used in holography to combine sample and reference beams, including planar beam splitters, cubic beam splitters, thin-film beam splitters, and polarizing beam splitters. However, thin-film beam splitters suffer from sinusoidal oscillation interference, making them unsuitable for holography. Planar beam splitters have anti-reflection coatings on their back surfaces, and cubic beam splitters are made by cementing two prisms coated with dielectric beam-splitting films, which leads to some intensity loss and prevents full utilization of the sample beam. Furthermore, since holography requires interference between the sample and signal beams, high precision is required in the flatness of the coatings and the parallelism of the cubic prism beam-splitting surfaces to avoid increasing noise. Larger beam spots require larger beam splitters, and the difficulty of achieving a flat coating increases significantly with size, greatly increasing the cost of the beam combining device. Beam splitters with beam spots exceeding two inches are almost unavailable on the market and must be custom-designed. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention proposes an off-axis holographic beam combining device and method based on a missing mirror. The missing mirror enables perfect beam combining in off-axis holography. This invention achieves a low-cost, easily adjustable off-axis angle, and no light intensity loss multi-beam beam combining scheme, which can further expand the application range of off-axis holography.

[0005] One object of the present invention is to provide an off-axis holographic beam combiner based on a missing type mirror.

[0006] The off-axis holographic beam combiner based on a missing mirror of the present invention includes: a light source, a beam splitter, a stage, a moving stage, a sample light reflector, a reference light reflector, a first focusing lens, a second focusing lens, a missing mirror, a missing mirror mounting bracket, an imaging lens, and a signal collection device; wherein, the sample is placed on the stage, the stage is mounted on the moving stage, and the moving stage can drive the stage and the sample to move in three dimensions; the second focusing lens is mounted on a translation stage, and the translation stage can drive the second focusing lens to move in the xy plane; the missing mirror is mounted on an adjustment bracket, and the adjustment bracket can adjust the height, xyz plane position, and pitch angle of the missing mirror;

[0007] The missing type mirror has a reflective part and a light-transmitting part. The reflective part is coated with a metal reflective film to reflect the light beam; the light-transmitting part does not block the light at all, and the light beam can pass through directly.

[0008] The light source emits laser light, which is split into two beams by a beam splitter: one beam serves as the sample light, and the other as the reference light. The sample light, after passing through the sample, carries sample information. This sample light, after being deflected by a sample light reflector, is then focused by a first focusing lens to form a focused beam. A missing-type reflector is placed at the focal plane of this focused beam, with its focal point located in the light-transmitting portion of the missing-type reflector. The sample light, carrying sample information, passes through the missing-type reflector without any intensity loss and becomes parallel light after passing through an imaging lens. The reference light is reflected by a reference light reflector and then focused by a second focusing lens onto the missing-type reflector. The focused reference light is reflected by the reflective surface of the missing-type reflector, resulting in high reflection efficiency and no intensity loss. The reflected reference light propagates to the imaging lens and becomes parallel light. The reference light and sample light then pass through the imaging lens and converge at the signal collection point. The reference beam and sample beam are combined at the detection surface, and the combined beam has an angle between them. The spots of the combined reference beam and sample beam coincide on the detection surface of the signal collection device, forming interference. The detector acquires the interference fringes formed by the combined beam. The angle between the combined reference beam and sample beam forms an off-axis hologram. The position of the second focusing lens in the xy plane is adjusted by the translation stage, adjusting the position of the reference beam incident on the second focusing lens and the position of the reference beam incident on the reflection part of the missing mirror after being focused by the second focusing lens, thereby adjusting the angle between the reference beam and sample beam entering the detection surface to adjust the density of the interference fringes. The height, horizontal position and pitch angle of the missing mirror are adjusted by the adjustment frame of the missing mirror, so that the spots of the reference beam with different incident angles coincide with the spots of the sample beam on the detection surface, realizing that the adjustment of the angle between the reference beam and sample beam and the adjustment of the spot coincidence are independent of each other.

[0009] The beam splitter uses a half-wave plate and a polarizing beam splitter prism. The laser beam first passes through the half-wave plate to the polarizing beam splitter prism. The polarizing beam splitter prism splits the laser beam into two beams, one of which serves as the sample light and the other beam propagates only in free space as the reference light. The intensity distribution of the two beams is adjusted by rotating the angle of the half-wave plate. For light sources with non-single polarization direction, the beam splitter also includes a polarizer, which is placed in front of the half-wave plate.

[0010] Since the sample light generally travels a long distance, the first focusing lens is a long focal length lens with a focal length of 150 mm or more; the second focusing lens is a short focal length lens with a focal length of less than 100 mm, so that the focusing surfaces of the sample light passing through the first focusing lens and the reference light passing through the second focusing lens are both at the surface of the missing type mirror.

[0011] The missing-type reflector proposed in this invention refers to a special reflector that is partially missing from a conventional reflector. Functionally, for multiple beams of light illuminating the missing-type reflector, it can simultaneously reflect one portion of the beam and transmit another. Structurally, relative to a basic planar shape, the shape of the missing-type reflector is partially missing, such as a semicircle or a ring. In a semicircular missing-type reflector, one side of the semicircle serves as the reflecting part, and the missing semicircle serves as the light-transmitting part. In a ring-shaped missing-type reflector, one side of the ring serves as the reflecting part, and the through-hole in the ring serves as the light-transmitting part.

[0012] The adjustment frame for the missing mirror is a five-axis adjustment frame, on which the missing mirror is mounted, allowing for adjustment of its x, y, and z-axis movement, tilt angle, and deflection angle. Alternatively, a support rod, sleeve, base, and three-dimensional adjustment frame can be used. The bottom end of the support rod is vertically mounted on the base, and the top end of the support rod is fitted with the three-dimensional adjustment frame, on which the missing mirror is placed. The height of the missing mirror is adjusted by extending or retracting the support rod, and the tilt angle and x, y-plane position of the missing mirror are adjusted by the three-dimensional adjustment frame. The three-dimensional adjustment frame uses a borderless mounting bracket to avoid obstructing the sample light.

[0013] The material of the reflective film depends on the wavelength and intensity of the light source; it can be a metal film or a dielectric film. Metal films can be made of gold, silver, or aluminum.

[0014] The light source is a laser light source, or a light source with a coherence length of more than 1m and coherence performance that enables multi-beam interference.

[0015] The signal collection device uses a camera.

[0016] Another objective of this invention is to propose an off-axis holographic beam combining method based on a missing mirror.

[0017] The off-axis holographic beam combining method based on a missing mirror of the present invention includes the following steps:

[0018] 1) Place the sample on the stage and set the stage on the moving stage. The moving stage can move the stage and the sample in three dimensions. Set the second focusing lens on the translation stage. The translation stage can move the second focusing lens in the xy plane. Set the missing mirror on the adjustment frame. The adjustment frame can adjust the height, xyz plane position and pitch angle of the missing mirror.

[0019] 2) The light source emits laser light, which is split into two beams by a beam splitter. One beam is used as the sample light, and the other beam is used as the reference light.

[0020] 3) After the sample light passes through the sample, the transmitted beam carries the sample information. The sample light carrying the sample information is deflected after passing through the sample light reflector and then focused by the first focusing lens to form a focused beam. A missing type reflector is placed at the focal plane of the focused beam. The focal point of the focused beam is located in the light-transmitting part of the missing type reflector. The sample light carrying the sample information passes through the missing type reflector without any loss of light intensity and becomes parallel light after passing through the imaging lens.

[0021] The reference light is reflected by the reference light mirror, and then focused by the second focusing lens onto the missing mirror. The focused reference light is reflected by the reflecting surface of the missing mirror. The reflection efficiency is high and there is no loss of light intensity. The reflected reference light propagates to the imaging lens and becomes parallel light after passing through the imaging lens.

[0022] 4) The reference light and the sample light are combined at the detection surface of the signal collection device after passing through the imaging lens. The combined reference light and the sample light have an angle between them. The light spots of the combined reference light and the sample light coincide on the detection surface of the signal collection device to form interference. The detector acquires the interference fringes formed by the combined beam. The combined reference light and the sample light have an angle to form off-axis holography.

[0023] 5) Adjust the position of the second focusing lens in the xy plane by adjusting the translation stage, adjust the position of the reference light incident on the second focusing lens and the position of the light incident on the reflection part of the missing mirror after being focused by the second focusing lens, and then adjust the angle between the reference light and the sample light entering the detection surface to adjust the density of the interference fringes.

[0024] 6) Adjust the height, horizontal position, and pitch angle of the missing mirror by placing the adjustment frame on it, so that the light spots of the reference light with different incident angles coincide with the light spots of the sample light on the detection surface, so that the adjustment of the angle between the reference light and the sample light and the adjustment of the light spot coincidence are independent of each other.

[0025] Advantages of this invention:

[0026] This invention employs a missing-type reflector to combine sample light and reference light. 1) During beam combining, the sample light is not obstructed in any way, and only the reference light is reflected, achieving a perfect beam combining scheme without loss of light intensity; 2) It is more conducive to achieving off-axis holography of the reference and sample lights. The missing-type reflector completely separates the difficult-to-adjust issues in the off-axis holographic optical path—namely, the alignment of the sample and reference lights on the detector and the adjustment of the off-axis angle between them—allowing for independent adjustment. By adjusting the mounting bracket of the missing-type reflector, spatial alignment of the reference and sample lights on the detector surface can be achieved; and by adjusting the position of the reference light illuminating the missing-type reflector... It can adjust the degree of separation between the sample light and the reference light in the frequency domain, that is, adjust the off-axis angle between the sample light and the reference light; by using a missing mirror, it realizes that the spatial coincidence and the frequency domain separation (adjustment of the off-axis angle) are divided into two processes for separate control, which solves the problem that the optical path of the beam combining part of off-axis holography is difficult to adjust; 3) The missing mirror beam combining device is compatible with any spot size, while the size of the beam splitter in the traditional prism beam combining scheme is related to the shape of the spot. When the system spot changes, the beam splitter needs to be replaced and the optical path needs to be rebuilt. The larger the beam splitter, the higher the cost. The missing mirror beam combining device is cheaper and suitable for any spot system. When the spot changes, there is no need to rebuild the optical path. Attached Figure Description

[0027] Figure 1 This is an optical path diagram of the off-axis holographic beam combiner based on a missing mirror according to the present invention;

[0028] Figure 2 This is a partial optical path diagram of the missing mirror in Embodiment 1 of the off-axis holographic beam combiner based on the missing mirror of the present invention;

[0029] Figure 3 This is a schematic diagram of the missing mirror in Embodiment 1 of the off-axis holographic beam combining device based on the missing mirror of the present invention, wherein (a) is a front view, (b) is a top view, and (c) is a left view;

[0030] Figure 4 This is a partial optical path diagram of the missing mirror in Embodiment 2 of the off-axis holographic beam combiner based on the missing mirror of the present invention;

[0031] Figure 5 This is a schematic diagram of the missing mirror in Embodiment 2 of the off-axis holographic beam combining device based on the missing mirror of the present invention, wherein (a) is a front view, (b) is a top view, and (c) is a left view. Detailed Implementation

[0032] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0033] like Figure 1 As shown, this embodiment of the off-axis holographic beam combiner based on a missing mirror includes: a light source 1, a beam splitter 2, a stage 4, a moving stage 5, a sample light reflector 6, a reference light reflector 7, a first focusing lens 8, a second focusing lens 9, a missing mirror 10, a missing mirror mounting bracket, an imaging lens 11, and a signal collection device 12. The sample 3 is placed on the stage, the surface of which is located in the xy plane. The stage is mounted on the moving stage 5, which allows the stage and sample to move in three dimensions. The second focusing lens 9 is mounted on a translation stage, which allows the second focusing lens 9 to move in the xy plane. The missing mirror 10 is mounted on an adjustment bracket, which allows adjustment of the height, xyz plane position, and pitch angle of the missing mirror 10. The signal collection device 12 uses a camera.

[0034] Functionally, for multiple beams of light illuminating the missing-type reflector 10, the missing-type reflector 10 can simultaneously reflect a portion of the beams and transmit another portion. Structurally, relative to a basic planar shape, the shape of the missing-type reflector 10 is partially missing; the missing-type reflector 10 has a reflecting portion 13 and a light-transmitting portion 14. The reflecting portion is coated with a metal reflective film to reflect the light beam; the light-transmitting portion does not obstruct the light, allowing the beam to pass through directly.

[0035] Light source 1 emits laser light, which is split into two beams by beam splitter 2: one beam serves as the sample beam, and the other as the reference beam. Before the focusing lens, the propagation directions of the reference beam and the sample beam are perpendicular to each other. The sample beam propagates towards the signal collecting device 12, while the reference beam propagates perpendicular to the signal collecting device 12. After passing through the sample, the transmitted beam carries sample information and is then deflected at the sample beam reflector 6. It is then focused by the first focusing lens 8, with the focal point being a point spot. A missing-type reflector 10 is placed at the focal plane of the focused beam, and the focal plane of the sample beam is located at the missing-type reflector. At point 10, the focal point of the focused beam is located in the light-transmitting portion of the missing mirror 10. The sample light carrying sample information passes through the missing mirror 10 without any intensity loss. The beam does not deflect and propagates towards the signal collecting device 12. After reaching the imaging lens 11, the focused beam is converted into a parallel beam and illuminates the detection surface of the signal collecting device 12. On the other hand, the reference light propagating vertically from the beam splitter 2 is reflected by the reference light mirror 7 and focused into a point spot by the second focusing lens 9. The focused reference spot is incident on the missing mirror 10. The reflective surface of the reflector 10 is reflected, causing the light beam to be deflected and propagate towards the signal collection device 12. The reflected light spot propagates to the imaging lens 11, from which parallel light is emitted. The reference light and sample light converge at the camera's detection surface after passing through the imaging lens 11, and the converged reference light and sample light have an angle between them. The light spots of the converged reference light and sample light coincide on the camera's detection surface, forming interference. The detector acquires the interference fringe data formed by the converged beam. The angle between the converged reference light and sample light forms an off-axis hologram. The second focusing lens 9 is adjusted by the translation stage at x The position of the y-plane is adjusted to change the position of the reference light incident on the second focusing lens 9 and the position of the light spot after focusing by the second focusing lens 9 incident on the reflective part of the missing mirror 10. This, in turn, adjusts the angle between the reference light and the sample light entering the detector surface, thereby adjusting the density of the interference fringes. The height, horizontal position, and pitch angle of the missing mirror 10 are adjusted by the adjustment frame of the missing mirror 10, so that the light spots of the reference light with different incident angles and the light spots of the sample light coincide on the detector surface. This makes the adjustment of the angle between the reference light and the sample light and the adjustment of the light spot coincidence independent of each other.

[0036] The beam splitter 2 employs a half-wave plate 21 and a polarizing beam splitter prism 22. The laser beam first passes through the half-wave plate to the polarizing beam splitter prism. The beam splitter prism splits the laser beam into two beams. One beam passes through the sample and carries sample information, and is called the sample light. The other beam only propagates in free space and serves as the reference light. The intensity distribution of the two beams is adjusted by rotating the wave plate angle. For light sources with non-single polarization direction, the beam splitter 2 also includes a polarizer, which is placed in front of the half-wave plate.

[0037] The missing mirror 10 adjustment frame consists of a support rod, a sleeve, a base, and a three-dimensional adjustment frame. The bottom end of the support rod is vertically mounted on the base, and the top end of the support rod is fitted with the three-dimensional adjustment frame, on which the missing mirror 10 is placed. The height of the missing mirror 10 is adjusted by extending or retracting the support rod, and the pitch angle and xy-plane position of the missing mirror 10 are adjusted by the three-dimensional adjustment frame. The three-dimensional adjustment frame must not obstruct the sample light and uses a borderless mounting bracket.

[0038] Example 1

[0039] like Figure 2 and 3 As shown, in this embodiment, the missing reflector 10 is annular, with an outer radius of one inch, an inner radius of 0.75 inches, and a thickness of 3 mm. The surface of the annular ring, serving as the reflective portion 13, is coated with a reflective film, resulting in high reflection efficiency and no light intensity loss. The through-hole in the center of the annular ring serves as the light-transmitting portion 14.

[0040] Example 2

[0041] like Figure 4 and 5 As shown, in this embodiment, the missing type reflector 10 includes an outer square shape and an inner circular through-hole. The outer square shape has a side length of one inch, and the inner circular through-hole has a diameter of 0.75 inches and a thickness of 3 mm. The surface of the outer square shape is coated with a reflective film as a reflective portion 13, and the inner circular through-hole serves as a light-transmitting portion 14.

[0042] Finally, it should be noted that the purpose of disclosing the embodiments is to help further understand the present invention. However, those skilled in the art will understand that various substitutions and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the present invention should not be limited to the content disclosed in the embodiments, and the scope of protection of the present invention is defined by the claims.

Claims

1. An off-axis holographic beam combiner based on a missing mirror, characterized in that, The off-axis holographic beam combiner includes: a light source, a beam splitter, a stage, a moving stage, a sample light reflector, a reference light reflector, a first focusing lens, a second focusing lens, a missing reflector, a missing reflector mounting bracket, an imaging lens, and a signal collection device. The sample is placed on the stage, which is mounted on the moving stage, allowing the stage and sample to move in three dimensions. The second focusing lens is mounted on a translation stage, which allows the second focusing lens to move in the xy-plane. The missing reflector is mounted on an adjustment bracket, which allows adjustment of the missing reflector's height, xyz-plane position, and pitch angle. The missing mirror has a reflective part and a light-transmitting part. The reflective part is coated with a metal reflective film to reflect the light beam. The light-transmitting part does not block the light and the light beam can pass through directly. The missing mirror is ring-shaped. In the ring-shaped missing mirror, one side of the ring serves as the reflective part, and the through hole in the ring serves as the light-transmitting part. The light source emits laser light, which is split into two beams by a beam splitter: one beam serves as the sample light, and the other as the reference light. The sample light, after passing through the sample, carries sample information. This sample light, after being deflected by a sample light reflector, is then focused by a first focusing lens to form a focused beam. A missing-type reflector is placed at the focal plane of this focused beam, with its focal point located in the light-transmitting portion of the missing-type reflector. The sample light, carrying sample information, passes through the missing-type reflector without any intensity loss and becomes parallel light after passing through an imaging lens. The reference light is reflected by a reference light reflector and then focused by a second focusing lens onto the missing-type reflector. The focused reference light is reflected by the reflective surface of the missing-type reflector, resulting in high reflection efficiency and no intensity loss. The reflected reference light propagates to the imaging lens and becomes parallel light. The reference light and sample light then pass through the imaging lens and converge at the signal collection point. The reference beam and sample beam are combined at the detection surface, and the combined beam has an angle between them. The spots of the combined reference beam and sample beam coincide on the detection surface of the signal collection device, forming interference. The detector acquires the interference fringes formed by the combined beam. The angle between the combined reference beam and sample beam forms an off-axis hologram. The position of the second focusing lens in the xy plane is adjusted by the translation stage, adjusting the position of the reference beam incident on the second focusing lens and the position of the reference beam incident on the reflection part of the missing mirror after being focused by the second focusing lens, thereby adjusting the angle between the reference beam and sample beam entering the detection surface to adjust the density of the interference fringes. The height, horizontal position and pitch angle of the missing mirror are adjusted by the adjustment frame of the missing mirror, so that the spots of the reference beam with different incident angles coincide with the spots of the sample beam on the detection surface, realizing that the adjustment of the angle between the reference beam and sample beam and the adjustment of the spot coincidence are independent of each other.

2. The off-axis holographic beam-combining device as described in claim 1, characterized in that, The beam splitting device uses a half-wave plate and a polarizing beam splitter prism. The laser first passes through the half-wave plate to the polarizing beam splitter prism. The polarizing beam splitter prism splits the laser into two beams, one of which serves as the sample light and the other beam propagates only in free space as the reference light. The intensity distribution of the two beams is adjusted by rotating the angle of the half-wave plate.

3. The off-axis holographic beam-combining device as described in claim 2, characterized in that, For light sources with non-single polarization direction, the beam splitting device further includes a polarizer, which is positioned in front of a half-wave plate.

4. The off-axis holographic beam-combining device as described in claim 1, characterized in that, The first focusing lens is a telephoto lens with a focal length of 150 mm or more; the second focusing lens is a short-focal-length lens with a focal length of 100 mm or less.

5. The off-axis holographic beam-combining device as described in claim 1, characterized in that, The adjustment frame for placing the missing mirror can be a five-axis adjustment frame; or a support rod, sleeve, base, and three-dimensional adjustment frame. The bottom end of the support rod is vertically mounted on the base, and the top end of the support rod is mounted on the three-dimensional adjustment frame, on which the missing mirror is placed. The height of the missing mirror is adjusted by extending and retracting the support rod, and the pitch angle and position of the missing mirror in the xy plane are adjusted by the three-dimensional adjustment frame.

6. The off-axis holographic beam-combining device as described in claim 5, characterized in that, The three-dimensional adjustment frame adopts a borderless mounting frame.

7. The off-axis holographic beam-combining device as described in claim 1, characterized in that, The metal reflective film is made of gold, silver, or aluminum.

8. The off-axis holographic beam-combining device as described in claim 1, characterized in that, The light source is a laser light source.

9. An off-axis holographic beam combining method for an off-axis holographic beam combining device based on a missing type mirror as described in claim 1, characterized in that, The off-axis holographic beam combining method includes the following steps: 1) Place the sample on the stage and set the stage on the moving stage. The moving stage can move the stage and the sample in three dimensions. Set the second focusing lens on the translation stage. The translation stage can move the second focusing lens in the xy plane. Set the missing mirror on the adjustment frame. The adjustment frame can adjust the height, xyz plane position and pitch angle of the missing mirror. 2) The light source emits laser light, which is split into two beams by a beam splitter. One beam is used as the sample light, and the other beam is used as the reference light. 3) After the sample light passes through the sample, the transmitted beam carries the sample information. The sample light carrying the sample information is deflected after passing through the sample light reflector and then focused by the first focusing lens to form a focused beam. A missing type reflector is placed at the focal plane of the focused beam, and the focal point of the focused beam is located at the light-transmitting part of the missing type reflector. The sample light carrying the sample information passes through the missing type reflector without any light intensity loss and becomes parallel light after passing through the imaging lens. The reference light is reflected by the reference light reflector and focused by the second focusing lens to the missing type reflector. The focused reference light is reflected by the reflective surface of the missing type reflector, with high reflection efficiency and no light intensity loss. The reflected reference light propagates to the imaging lens and becomes parallel light after passing through the imaging lens. 4) The reference light and the sample light are combined at the detection surface of the signal collection device after passing through the imaging lens. The combined reference light and the sample light have an angle between them. The light spots of the combined reference light and the sample light coincide on the detection surface of the signal collection device to form interference. The detector acquires the interference fringes formed by the combined beam. The angle between the combined reference light and the sample light forms an off-axis hologram. 5) Adjust the position of the second focusing lens in the xy plane by adjusting the translation stage, adjust the position of the reference light incident on the second focusing lens and the position of the light incident on the reflection part of the missing mirror after being focused by the second focusing lens, and then adjust the angle between the reference light and the sample light entering the detection surface to adjust the density of the interference fringes. 6) Adjust the height, horizontal position, and pitch angle of the missing mirror by placing the adjustment frame on it, so that the light spots of the reference light with different incident angles coincide with the light spots of the sample light on the detection surface, so that the adjustment of the angle between the reference light and the sample light and the adjustment of the light spot coincidence are independent of each other.

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