A method for detecting the optical path difference of a prism in a self-referencing interferometer

Abstract

The present invention provides a method for detecting the optical path difference of a self-referencing interferometer prism, comprising: light emitted by a white light source enters a polarization beam splitter prism and is split into two polarized beams; the self-referencing interferometer prism is installed above the polarization beam splitter prism; a first reflector and a second reflector are installed on a translation stage; a beam splitter prism is disposed below the self-referencing interferometer prism; a first half-wave plate is disposed on the optical path between the polarization beam splitter prism and the self-referencing interferometer prism; and a second half-wave plate is disposed on the optical path between the polarization beam splitter prism and the self-referencing interferometer prism; the optical path of the first prism in the self-referencing interferometer prism is measured to obtain a displacement distance L1 of the translation stage from an initial position; the optical path of the second prism in the self-referencing interferometer prism is measured to obtain a displacement distance L2 of the translation stage from the initial position; and the optical path difference of the self-referencing interferometer prism is calculated based on L1 and L2. The present invention can achieve accurate measurement of the optical path difference of the self-referencing interferometer prism.

Description

Technical Field

[0001] The present invention relates to the technical field of optical measurement, in particular to a method for detecting the optical path difference of a prism of a self-reference interferometer. Background Art

[0002] In a phase grating position measurement system based on the principle of self-referencing interferometry, the grating diffracted light is split and reflected by the self-referencing interferometer prism. Since the self-referencing interferometer prism is composed of two prisms glued together, the optical path lengths of the light propagating will no longer be equal, resulting in an optical path difference. This in turn causes a phase difference, resulting in increased background light on the detector and decreased contrast of the interference signal, ultimately significantly affecting measurement accuracy. Therefore, it is necessary to strictly control the optical path difference of the self-referencing interferometer prism in phase grating position measurement systems and adopt necessary methods to detect the optical path difference to ensure its measurement accuracy.

[0003] Existing methods for measuring prism optical path differences are limited; the most common approach involves measuring the optical path difference between the prism under test and a reference lens. Self-referencing interferometer prisms are constructed by gluing together two prisms with different shapes. Each prism has a light beam propagating through it, and each beam propagates not only through the prisms but also through the glued layer. Due to the unique structure of self-referencing interferometer prisms, measuring their optical path difference is difficult with existing technologies. Summary of the Invention

[0004] The object of the present invention is to provide a method for detecting the optical path difference of a self-referencing interferometer prism, which can solve the problem in the prior art that it is difficult to detect the optical path difference due to the structural particularity of the self-referencing interferometer prism.

[0005] The present invention provides a method for detecting the optical path difference of a prism of a self-referencing interferometer, comprising:

[0006] The light emitted by the white light source is vertically incident from the center of the polarization splitter prism and is split into the first polarization light and the second polarization light;

[0007] Installing a self-referencing interferometer prism above the polarization beam splitter prism so that the first polarized light can be vertically incident from an incident plane of the self-referencing interferometer prism;

[0008] A first reflector and a second reflector are mounted on the translation stage, respectively, so that the light of the second polarized light is reflected by the first reflector and the second reflector in sequence, and the incident light of the first reflector and the outgoing light of the second reflector are parallel to each other;

[0009] A beam splitter prism is provided below the self-referencing interferometer prism, so that the outgoing light of the second reflector and the outgoing light of the self-referencing interferometer prism are respectively incident on the beam splitter prism and respectively reach the detector after being transmitted and reflected by the beam splitter prism;

[0010] A first half-wave plate is provided on the optical path between the polarization beam splitter prism and the self-referencing interferometer prism, and a second half-wave plate is provided on the optical path between the polarization beam splitter prism and the first reflecting mirror;

[0011] Measuring the optical path of the first prism in the self-referencing interferometer prism, adjusting the translation stage to move along the direction of the incident light of the first reflector until the central interference fringe is white and the interference fringes on both sides are colored on the detector, and obtaining the displacement distance L1 of the translation stage from the initial position;

[0012] Measuring the optical path of the second prism in the self-referencing interferometer prism, adjusting the translation stage to move along the direction of the incident light from the first reflector until the central interference fringe is white and the interference fringes on both sides are colored on the detector, and obtaining the displacement distance L2 of the translation stage from the initial position;

[0013] Based on the displacement distance L1 and the displacement distance L2, the optical path difference of the self-referencing interferometer prism is calculated and obtained.

[0014] According to a method for detecting the optical path difference of a self-referencing interferometer prism provided by the present invention, the first polarized light separated by the white light source through the polarization splitting prism is S-polarized light, and the S-polarized light enters the incident surface of the self-referencing interferometer prism after passing through the first half-wave plate.

[0015] According to a method for detecting the optical path difference of a self-referencing interferometer prism provided by the present invention, the second polarized light separated by the white light source through the polarization splitting prism is P-polarized light, and the P-polarized light reaches the first reflector after passing through the second half-wave plate.

[0016] According to a method for detecting the optical path difference of a self-referencing interferometer prism provided by the present invention, the initial position of the first half-wave plate is perpendicular to the incident direction of the first polarized light, and the initial position of the second half-wave plate is perpendicular to the incident direction of the second polarized light.

[0017] According to a method for detecting the optical path difference of a prism of a self-referencing interferometer provided by the present invention, when measuring the optical path of a first prism in the prism of the self-referencing interferometer, the method comprises:

[0018] Adjusting the first half-wave plate so that the fast axis of the first half-wave plate forms an angle of 45° with the vibration direction of the first polarized light;

[0019] The first polarized light becomes P polarized light after passing through the first half-wave plate, and then enters the self-referencing interferometer prism from the incident surface of the second prism. After multiple reflections in the first prism in the self-referencing interferometer prism, it is transmitted through the polarization splitting surface of the first prism and then emitted through the incident surface of the second prism to enter the splitting prism.

[0020] Adjusting the second half-wave plate so that the fast axis of the second half-wave plate forms an angle of 0° with the vibration direction of the second polarized light;

[0021] The second polarized light remains as P polarized light after passing through the second half-wave plate, and then enters the beam splitter prism after being reflected by the first reflector and the second reflector in sequence.

[0022] According to a method for detecting the optical path difference of a prism of a self-referencing interferometer provided by the present invention, when measuring the optical path of a second prism in the prism of the self-referencing interferometer, the method comprises:

[0023] Adjusting the first half-wave plate so that the fast axis of the first half-wave plate forms an angle of 0° with the vibration direction of the first polarized light;

[0024] The first polarized light remains S-polarized light after passing through the first half-wave plate, and then enters the self-referencing interferometer prism from the incident surface of the second prism. After multiple reflections by the second prism in the self-referencing interferometer prism, it is reflected by the polarization splitting surface of the second prism and then emitted through the incident surface of the second prism to enter the splitting prism.

[0025] Adjusting the second half-wave plate so that the fast axis of the second half-wave plate forms an angle of 45° with the vibration direction of the second polarized light;

[0026] The second polarized light is converted into S polarized light after passing through the second half-wave plate, and then is reflected by the first reflector and the second reflector in sequence before entering the beam splitter prism.

[0027] According to a method for detecting the optical path difference of a self-referencing interferometer prism provided by the present invention, when installing the self-referencing interferometer prism, it is necessary to adjust and determine the position where the incident light enters the self-referencing interferometer prism.

[0028] According to a method for detecting the optical path difference of a prism of a self-referencing interferometer provided by the present invention, the optical path difference of the prism of the self-referencing interferometer is calculated by the following optical path difference calculation formula:

[0029] OPD = n × ΔL;

[0030] ΔL=L2-L1;

[0031] Wherein, OPD is the optical path difference of the self-referencing interferometer prism; n is the refractive index of light.

[0032] The method for detecting the optical path difference of a prism of a self-referencing interferometer provided by the present invention utilizes the Mach-Zehnder interference principle and, through a special arrangement of a prism, a polarization beam splitter, a first reflector, a second reflector, a beam splitter, a first half-wave plate, and a second half-wave plate of the self-referencing interferometer, changes the polarization state of light respectively through two half-wave plates during detection, and can respectively measure the optical path of the first prism and the second prism in the self-referencing interferometer. Since a white light source is used as a light source, the position of zero optical path difference can be accurately determined by observing white light interference fringes on a detector, thereby achieving precise measurement of the optical path difference of the prism of the self-referencing interferometer through calculation. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0034] Figure 1 2. A front view of a self-referencing interferometer prism according to an embodiment of the present invention;

[0035] Figure 2 1 is a left side view of a self-referencing interferometer prism according to an embodiment of the present invention;

[0036] Figure 3 is a top view of a self-referencing interferometer prism in an embodiment of the present invention;

[0037] Figure 4 Schematic diagram of the detection state of the optical path difference of the prism of the self-referencing interferometer in an embodiment of the present invention.

[0038] Description of reference numerals:

[0039] SRI1, first prism; 101, roof surface 1; 102, roof surface 2; 103a, bottom surface 1; 103b, exit surface; 104, polarization splitting surface 1;

[0040] SRI2, second prism; 201, roof surface three; 202, roof surface four; 203, bottom surface two; 204, polarization splitting surface two; 205, incident surface; 300, bonding layer;

[0041] 400, polarization zero; 401, polarization one; 402, polarization two; 403, polarization three; 404, polarization four; 405, polarization five; 406, polarization six; 407, polarization seven;

[0042] S1, white light source; PBS, polarization beam splitter; HW1, first half-wave plate; HW2, second half-wave plate; M1, first reflector; M2, second reflector; BS, beam splitter; D1, detector; UDP, translation stage. DETAILED DESCRIPTION

[0043] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0044] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like to indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operate in a specific direction, and therefore should not be understood as limiting the present invention.

[0045] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the said features. In the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined. In addition, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a communication between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to the specific circumstances.

[0046] like Figure 1As shown, in the method for detecting the optical path difference of a self-referencing interferometer prism according to an embodiment of the present invention, the self-referencing interferometer prism used is composed of a first prism SRI1 and a second prism SRI2, wherein the first prism SRI1 includes a ridge surface 101, a ridge surface 202, a bottom surface 103a, an exit surface 103b and a polarization splitting surface 104, and the second prism SRI2 includes a ridge surface 301, a ridge surface 402, a bottom surface 203, a polarization splitting surface 204 and an incident surface 205, wherein a polarization splitting film is coated between the polarization splitting surface 104 and the polarization splitting surface 204 and glued together to form a glue layer 300.

[0047] Polarized light 0 400 is incident on incident surface 205, and is split by polarization splitting surface 204 into a transmitted polarized light 1 401 and a reflected polarized light 2 402. These polarized light 1 401 then enters first prism SRI1 and second prism SRI2, respectively. Polarized light 1 401 is sequentially reflected by roof surface 101, bottom surface 103a, and roof surface 2 102 to produce polarized light 3 403. Polarized light 1 401 is then incident on polarization splitting surface 104 again, reflected by polarization splitting surface 104, and then emitted from exit surface 103b to produce polarized light 5 405. Polarized light 2 402 is then sequentially reflected by roof surface 3 201, bottom surface 203, and roof surface 4 202 to produce polarized light 4 404. Polarized light 2 402 is then incident on polarization splitting surface 204 again, transmitted by polarization splitting surface 204, and then emitted from exit surface 103b to produce polarized light 6 406. Polarized light five 405 and polarized light six 406 are combined into polarized light seven 407 .

[0048] like Figure 2 As shown, polarized light 401 is reflected by roof surface 101, bottom surface 103a, and roof surface 2 102 in sequence, and is incident on polarization splitting surface 104 again in a vertical downward direction. After being reflected by polarization splitting surface 104, it is emitted in a direction perpendicular to the exit surface 103b.

[0049] like Figure 3 As shown, polarized light 2 402 is reflected by roof surface 3 201, bottom surface 203, and roof surface 4 202 in sequence, and is incident on polarization splitting surface 2 204 again in a horizontal left direction. After being transmitted through polarization splitting surface 204, it is emitted in a direction perpendicular to the exit surface 103b.

[0050] The polarization direction of polarized light 0 400 forms a 45° angle with the P polarization direction of the polarization splitting plane. Polarized light 1 401 and polarized light 2 402 are polarized parallel and perpendicular, respectively, to the incident plane formed by polarized light 0 400 and the polarization splitting plane. After reflection from the first prism SRI1 and the second prism SRI2, polarized light 1 401 and polarized light 2 402 undergo a 90° rotation in their polarization directions, exiting coaxially as polarized light 5 405 and polarized light 6 406, which combine to form polarized light 7 407.

[0051] After the polarization splitting surface 104 of the first prism SRI1 and the polarization splitting surface 204 of the second prism SRI2 are coated with polarization splitting films, the path l2 of the light in the second prism SRI2 is: AB→BC→CD→DE→EF→FL→LM, where AB is polarization zero 400, BC is polarization two 402, CD is the reflected light transmitted from the ridge surface three 201 to the bottom surface two 203, DE is the reflected light transmitted from the bottom surface two 203 to the ridge surface four 202, EF is polarization four 404, FL is the light transmitted in the adhesive layer, and LM is polarization six 406. The path l1 of the light in the first prism SRI1 is: AB→BG→GH→HI→IJ→JK→KM, where AB is polarization zero 400, BG is the light transmitted in the adhesive layer, GH is polarization one 401, HI is the reflected light transmitted from the ridge surface one 101 to the bottom surface one 103a, IJ is the reflected light transmitted from the bottom surface one 103a to the ridge surface two 102, JK is polarization three 403, and KM is polarization five 405.

[0052] like Figure 4 As shown, the method for detecting the optical path difference of a prism in a self-referencing interferometer according to an embodiment of the present invention specifically includes the following steps:

[0053] The light emitted by the white light source S1 is vertically incident on the center of the polarization beam splitter prism PBS and is split into a first polarized light and a second polarized light.

[0054] A self-referencing interferometer prism is installed above the polarization beam splitter prism PBS so that the first polarized light can be vertically incident on the incident surface of the self-referencing interferometer prism.

[0055] A first reflector M1 and a second reflector M2 are respectively installed on the translation stage UDP, so that the second polarized light is reflected by the first reflector M1 and the second reflector M2 in sequence, and the incident light of the first reflector M1 and the outgoing light of the second reflector M2 are parallel to each other.

[0056] A beam splitter prism BS is provided below the self-referencing interferometer prism, so that the outgoing light from the second reflector M2 and the outgoing light from the self-referencing interferometer prism enter the beam splitter prism BS respectively, and reach the detector D1 after being transmitted and reflected by the beam splitter prism BS respectively.

[0057] A first half-wave plate HW1 is arranged on the optical path between the polarization splitter prism PBS and the self-referencing interferometer prism, and a second half-wave plate HW2 is arranged on the optical path between the polarization splitter prism PBS and the first reflector M1. The polarization state of light can be changed respectively by the first half-wave plate HW1 and the second half-wave plate HW2.

[0058] When measuring the optical path of the first prism SRI1 in the self-referencing interferometer prism, adjust the translation stage UDP and move it along the direction of the incident light from the first reflector M1 until the central interference fringe is white and the interference fringes on both sides are colored on the detector D1. At this time, the displacement distance L1 of the translation stage UDP from the initial position is obtained.

[0059] When measuring the optical path of the second prism SRI2 in the self-referencing interferometer prism, adjust the translation stage UDP and move it along the direction of the incident light from the first reflector M1 until the central interference fringe is white and the interference fringes on both sides are colored on the detector D1. At this time, the displacement distance L2 of the translation stage UDP from the initial position is obtained.

[0060] Based on the above displacement distance L1 and displacement distance L2, the optical path difference of the self-reference interferometer prism is calculated.

[0061] The optical path difference of the self-referencing interferometer prism is calculated using the following optical path difference calculation formula:

[0062] OPD = n × ΔL; ΔL = L2 - L1;

[0063] Where OPD is the optical path difference of the self-referencing interferometer prism; n is the refractive index of light.

[0064] Therefore, the method for detecting the optical path difference of the self-referencing interferometer prism in an embodiment of the present invention utilizes the Mach-Zehnder interference principle. Through the special arrangement of the self-referencing interferometer prism, the polarization beam splitter prism PBS, the first reflector M1, the second reflector M2, the beam splitter prism BS, the first half-wave plate HW1, and the second half-wave plate HW2, the polarization state of light is changed respectively by two half-wave plates during detection. The optical path of the first prism SRI1 and the second prism SRI2 in the self-referencing interferometer can be measured respectively. Since the light source adopts the white light source S1, the position of the zero optical path difference can be accurately determined by observing the white light interference fringes on the detector D1, and then the accurate measurement of the optical path difference of the self-referencing interferometer prism is achieved through calculation.

[0065] Specifically, the initial position of the first half-wave plate HW1 is perpendicular to the incident direction of the first polarized light, and the initial position of the second half-wave plate HW2 is perpendicular to the incident direction of the second polarized light.

[0066] The first polarized light generated by the polarization beam splitter PBS from the white light source S1 is S-polarized light. This S-polarized light then passes through the first half-wave plate HW1 and enters the incident plane of the self-referencing interferometer prism. During detection, the polarization state of the first polarized light can be changed by rotating the first half-wave plate HW1.

[0067] The second polarized light generated by the white light source S1 after being split by the polarization beam splitter PBS is P polarized light, which passes through the second half-wave plate HW2 and reaches the first reflector M1. During detection, the polarization state of the second polarized light can be changed by rotating the second half-wave plate HW2.

[0068] Specifically, when installing the self-referencing interferometer prism, it is necessary to adjust and determine the position at which the incident light enters the self-referencing interferometer prism. When the incident light into the self-referencing interferometer prism is 45° linearly polarized light, the light propagates through both the first prism SRI1 and the second prism SRI2. By adjusting the position of the self-referencing interferometer prism until the exit spots of polarized light 5 405 and polarized light 6 406 coincide, it can be determined that this position is the position at which the incident light enters the self-referencing interferometer prism.

[0069] Specifically, the outgoing light from the second reflector M2 and the outgoing light from the self-referencing interferometer prism intersect in the beam splitter prism BS and are respectively transmitted and reflected to form overlapping outgoing light, which then reaches the detector D1.

[0070] Furthermore, the optical path where the first reflector M1 and the second reflector M2 are located is set as the reference optical path, and the optical path where the first prism SRI1 and the second prism SRI2 are located is set as the measurement optical path.

[0071] When measuring the optical path length of the first prism SRI1 in the self-referencing interferometer prism, the following steps are included:

[0072] In the measurement optical path, the first half-wave plate HW1 is adjusted so that its fast axis forms a 45° angle with the vibration direction of the first polarized light. This converts the first polarized light into P-polarized light after passing through the first half-wave plate HW1 and then enters the self-referencing interferometer prism. Incident light enters the second prism SRI2 perpendicularly from the incident plane 205, passes through the second polarization splitting plane 204 of the second prism SRI2, and then enters the first prism SRI1. Ideally, after three reflections, polarized light 403 is completely converted to S-polarized light. This light then reflects through the first polarization splitting plane 104 of the first prism SRI1 and exits as polarized light 405. However, due to the influence of the adhesive layer, the small polarization extinction of the polarization splitting film, and processing errors, a portion of the polarized light 403 is still P-polarized light. After being transmitted through the polarization splitting plane 104 of the first prism SRI1, it is emitted through the incident plane 205 of the second prism SRI2 and enters the splitter prism BS. This measurement method uses this stray light to measure the optical path difference.

[0073] In the reference optical path, the second half-wave plate HW2 is adjusted so that the fast axis of the second half-wave plate HW2 forms an angle of 0° with the vibration direction of the second polarized light. Then, the second polarized light remains P-polarized light after passing through the second half-wave plate HW2, and then enters the beam splitter prism BS after being reflected by the first reflector M1 and the second reflector M2 in sequence.

[0074] That is, the two beams of P-polarized light emitted by the second reflector M2 and the self-referencing interferometer prism are respectively transmitted and reflected by the beam splitter BS before reaching the detector D1. Since the detector D1 is a color fringe image detector, fringes of different colors can be observed through the detector D1.

[0075] During the detection process, it is necessary to adjust the positions of the first reflector M1 and the second reflector M2 through the displacement platform UDP. The displacement platform UDP adopts a nanometer-level ultra-precision displacement platform, which can move back and forth along the direction of the incident light of the first reflector M1 until the middle interference fringe is white and the interference fringes on both sides are colored on the detector D1. At this time, the distance of the displacement platform UDP relative to its initial position is the obtained displacement distance L1.

[0076] When measuring the optical path length of the second prism SRI2 in the self-referencing interferometer prism, the following steps are included:

[0077] In the measurement optical path, the first half-wave plate HW1 is adjusted so that its fast axis forms a 0° angle with the vibration direction of the first polarized light. This allows the first polarized light to remain S-polarized after passing through the first half-wave plate HW1 and then enter the self-referencing interferometer prism. Incident light enters the second prism SRI2 perpendicularly from the incident surface 205 and is then reflected by the second polarization splitting surface 204 of the second prism SRI2. Ideally, after three reflections, the polarized light 404 is completely converted to P-polarized light, which is then transmitted through the second polarization splitting surface 204 of the second prism SRI2 and then emitted. However, due to the effects of the adhesive layer, the relatively small polarization extinction ratio of the polarization splitting film, and manufacturing errors, a portion of the polarized light 404 remains S-polarized. After being reflected by the second polarization splitting surface 204 of the second prism SRI2, it is emitted through the incident surface 205 and enters the beam splitting prism BS. The measurement method utilizes this stray light to measure the optical path difference.

[0078] In the reference optical path, the second half-wave plate HW2 is adjusted so that the fast axis of the second half-wave plate HW2 forms a 45° angle with the vibration direction of the second polarized light. Then, the second polarized light becomes S-polarized light after passing through the second half-wave plate HW2, and then is reflected by the first reflector M1 and the second reflector M2 in sequence before entering the beam splitter prism BS.

[0079] That is, the two beams of S-polarized light emitted by the second reflector M2 and the self-referencing interferometer prism are transmitted and reflected by the beamsplitter BS, respectively, before arriving at detector D1. During the detection process, the positions of the first reflector M1 and the second reflector M2 are adjusted using the translation stage UDP until the central interference fringe is white and the interference fringes on the sides are colored on detector D1. The distance at which the translation stage UDP is located relative to its initial position at this point is the acquired displacement distance L2.

[0080] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for detecting the optical path difference of a prism in a self-referencing interferometer, characterized in that: include: The light emitted by the white light source is vertically incident from the center of the polarization splitter prism and is split into the first polarization light and the second polarization light; Installing a self-referencing interferometer prism above the polarization beam splitter prism so that the first polarized light can be vertically incident from an incident plane of the self-referencing interferometer prism; A first reflector and a second reflector are mounted on the translation stage, respectively, so that the light of the second polarized light is reflected by the first reflector and the second reflector in sequence, and the incident light of the first reflector and the outgoing light of the second reflector are parallel to each other; A beam splitter prism is provided below the self-referencing interferometer prism, so that the outgoing light of the second reflector and the outgoing light of the self-referencing interferometer prism are respectively incident on the beam splitter prism and respectively reach the detector after being transmitted and reflected by the beam splitter prism; A first half-wave plate is provided on the optical path between the polarization beam splitter prism and the self-referencing interferometer prism, and a second half-wave plate is provided on the optical path between the polarization beam splitter prism and the first reflecting mirror; Measuring the optical path of the first prism in the self-referencing interferometer prism, adjusting the translation stage to move along the direction of the incident light of the first reflector until the central interference fringe is white and the interference fringes on both sides are colored on the detector, and obtaining the displacement distance L1 of the translation stage from the initial position; Measuring the optical path of the second prism in the self-referencing interferometer prism, adjusting the translation stage to move along the direction of the incident light from the first reflector until the central interference fringe is white and the interference fringes on both sides are colored on the detector, and obtaining the displacement distance L2 of the translation stage from the initial position; Based on the displacement distance L1 and the displacement distance L2, the optical path difference of the self-referencing interferometer prism is calculated and obtained.

2. The method for detecting the optical path difference of a prism in a self-referencing interferometer according to claim 1, wherein: The first polarized light separated by the white light source through the polarization beam splitting prism is S-polarized light, and the S-polarized light enters the incident surface of the self-referencing interferometer prism after passing through the first half-wave plate.

3. The method for detecting the optical path difference of a prism in a self-referencing interferometer according to claim 2, wherein: The second polarized light separated by the polarization beam splitting prism from the white light source is P polarized light, and the P polarized light reaches the first reflector after passing through the second half-wave plate.

4. The method for detecting the optical path difference of a prism in a self-referencing interferometer according to claim 3, wherein: An initial position of the first half-wave plate is perpendicular to the incident direction of the first polarized light, and an initial position of the second half-wave plate is perpendicular to the incident direction of the second polarized light.

5. The method for detecting the optical path difference of a prism in a self-referencing interferometer according to claim 1, wherein: When measuring the optical path length of the first prism in the self-referencing interferometer prism, the method includes: Adjusting the first half-wave plate so that the fast axis of the first half-wave plate forms an angle of 45° with the vibration direction of the first polarized light; The first polarized light becomes P polarized light after passing through the first half-wave plate, and then enters the self-referencing interferometer prism from the incident surface of the second prism. After multiple reflections in the first prism in the self-referencing interferometer prism, it is transmitted through the polarization splitting surface of the first prism and then emitted through the incident surface of the second prism to enter the splitting prism.

6. The method for detecting the optical path difference of a prism in a self-referencing interferometer according to claim 5, wherein: Also includes: Adjusting the second half-wave plate so that the fast axis of the second half-wave plate forms an angle of 0° with the vibration direction of the second polarized light; The second polarized light remains as P polarized light after passing through the second half-wave plate, and then enters the beam splitter prism after being reflected by the first reflector and the second reflector in sequence.

7. The method for detecting the optical path difference of a prism in a self-referencing interferometer according to claim 1, wherein: When measuring the optical path length of the second prism in the self-referencing interferometer prism, the method includes: Adjusting the first half-wave plate so that the fast axis of the first half-wave plate forms an angle of 0° with the incident direction of the first polarized light; The first polarized light remains S-polarized light after passing through the first half-wave plate, and then enters the self-referencing interferometer prism from the incident surface of the second prism. After multiple reflections in the second prism in the self-referencing interferometer prism, it is reflected by the polarization splitting surface of the second prism and then emitted through the incident surface of the second prism to enter the splitting prism.

8. The method for detecting the optical path difference of a prism in a self-referencing interferometer according to claim 7, wherein: Also includes: Adjusting the second half-wave plate so that the fast axis of the second half-wave plate forms an angle of 45° with the vibration direction of the second polarized light; The second polarized light is converted into S polarized light after passing through the second half-wave plate, and then is reflected by the first reflector and the second reflector in sequence before entering the beam splitter prism.

9. The method for detecting the optical path difference of a prism in a self-referencing interferometer according to claim 1, wherein: When installing the self-referencing interferometer prism, it is necessary to adjust and determine the position where the incident light enters the self-referencing interferometer prism.

10. The method for detecting the optical path difference of a prism in a self-referencing interferometer according to claim 1, wherein: The optical path difference of the self-referencing interferometer prism is calculated by the following optical path difference calculation formula: OPD = n × ΔL; ΔL=L2-L1; Wherein, OPD is the optical path difference of the self-referencing interferometer prism; n is the refractive index of light.

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